目前国内有关避税经济后果研究较少，对非投资效率的影响更少并且说法不一。由于2010年的资源税从价计征改革，资源型企业税负加重，资源型企业避税是为企业节省累积现金流因而“积少成多”，还是企业因避税引发更多的代理问题“因小失大”？本文构建了“企业避税—代理成本—非效率投资”的中介效应模型，运用2010-2017年资源型企业面板数据，实证检验了资源型企业避税对非效率投资的影响及其作用机制。研究发现：资源型企业避税会导致企业非效率投资并增加第一类代理成本和第二类代理成本；第一类代理成本在企业避税与非效率投资之间有遮掩效应，第二类代理成本在企业避税与非效率投资之间起部分中介的作用。内部控制缺陷是企业避税影响非效率投资的调节变量，企业内部控制缺陷越大，企业避税对非效率投资的正向作用越大。内部控制缺陷越小，企业避税对非效率投资的正向作用越小。

    At present, few people study the economic consequences of tax avoidance in China, and there is less influence on investment efficiency and different people have different opinions. The level of investment efficiency not only affects the speed of economic growth, but also is closely related to the level of economic strength of various countries. However, inefficient investments such as over-investment and under-investment are common in listed companies in China. Scholars at home and abroad mainly study the causes of inefficient investment from the perspective of financing constraints and free cash flow and they pay little attention to the factors affecting the investment efficiency of resource-based enterprises. 
    China is a resource-based country, and there are many resource-based enterprises whose main business is the development and utilization of natural resources, which have made outstanding contributions to China′s economic development. However, due to over-exploitation of resources by resource-based enterprises, resulting in overcapacity and distorted allocation, inefficient investment by enterprises has become more and more common. At the same time, the environmental regulation policy implemented by the State increases the production cost and tax burden of resource-based enterprises and affects their tax activities. Whether resource-based enterprises can alleviate the pressure of capital through tax avoidance thus affecting the efficiency of investment, is a problem that scholars should have paid extensive attention to. Starting from the reform of ad valorem taxation of oil and natural gas in 2010, China has continuously expanded the scope of resource tax collection. The tax burden of resource-based enterprises has increased and their profitability has decreased, triggering the motivation of resource-based enterprises to avoid tax. Tax avoidance by enterprises is regarded by many enterprises as a way to increase enterprise income and improve performance. In the short term, this will enable enterprises to obtain more capital flow. But in the long run, tax avoidance will increase information asymmetry within the enterprise, lead to serious agency problems and increase agency costs. Do resource-based enterprises "gain from a small amount" by tax avoidance because it saves accumulated cash flow for enterprises, or does enterprises′ tax avoidance behavior cause more agency problems which lead to "lose a lot"? Research by scholars shows that tax avoidance will affect enterprise value, agency cost, equity financing cost and so on, but there is little research on the impact of tax avoidance on inefficient investment and the path of impact. 
    In view of this, this paper uses the panel data of resource-based enterprises from 2010 to 2017 to empirically test the impact of resource-based enterprise tax avoidance on inefficient investment and its mechanism. On the one hand, we introduce the mediate variable of agency cost, constructs a mediating effect model of "enterprise tax avoidance-agency cost-inefficient investment", empirically tests the influence of tax avoidance of resource-based enterprises on inefficient investment and two types of agency cost, and discusses the mediating roles of two types of agency cost in the relationship between tax avoidance and inefficient investment. Therefore, Hypothesis 1, Hypothesis 2，and Hypothesis 3 are put forward. On the other hand, we introduce the moderate variable of internal control defects, construct a moderating effect model of "tax avoidance-internal control defects-inefficient investment". Therefore, Hypothesis 4 is put forward. In order to make the conclusion more reliable, the models involved in the regression were tested by horseman and using differential GMM Method to Overcome Endogenous Problem. 
    The test results showed: (1) Tax avoidance behavior of resource-based enterprises will aggravate the information asymmetry and principal-agent problem within the enterprises, at the same time, it will lead to insufficient incentives for managers, increase opportunism behavior of managers and shareholders, and lead to more serious inefficient investment. (2) For tax avoidance by enterprises, because they usually use related party transactions or private transactions to reduce transaction prices and the amount of income used to calculate income tax, it is closely related to the second type of agency costs. On the contrary, the first type of agency costs plays less role. Research shows that the second kind of agency cost is the intermediary variable between tax avoidance and inefficient investment. The concealment of information brought by tax avoidance will stimulate shareholders′ irrational investment behavior, increase the second kind of agency cost, and thus reduce the investment efficiency of enterprises. (3) Internal control defects will affect the relationship between tax avoidance and inefficient investment, that is, the greater the internal control defects, the more inefficient investment caused by tax avoidance. The smaller the defect of internal control, the less inefficient investment caused by tax avoidance. 
    The conclusion of this paper is conducive to a deep understanding of the relationship between tax avoidance and inefficient investment by resource-based enterprises. For enterprises, tax avoidance does not enable enterprises to obtain long-term benefits, but will reduce the investment efficiency of enterprises, "for small losses, big losses". Moreover, when enterprises have internal control defects, the inefficient investment is more serious, so they should pay attention to the effective operation of the internal control mechanism, optimize the allocation of resources, and reduce the inefficient investment of the enterprise.