贸易自由化与就业是国际贸易的核心问题，然而对贸易自由化如何影响企业雇佣技能结构的研究却很少。本文基于世界银行对中东欧和中亚地区26个国家营商环境调查的企业水平数据，考察了贸易自由化对企业雇佣技能结构的影响。结果表明贸易自由化会促使企业雇佣更高比例的高技能劳动力，其影响机制主要是贸易自由化会加剧市场竞争和产业结构升级进而加强了企业对高技能劳动力的需求。本文结论意味着贸易自由化促进了企业雇佣技能结构改善，提高了劳动力市场的配置效率，进而间接给出了贸易自由化导致国民福利改进的一种新的途径。

    The issue of trade liberalization and employment reflects the production structure of a country, the level of industry development and the gain of different types of labor in trade. It is not only one of the core issues in the field of international trade, but also the consideration of industrial policies, trade policies and foreign investment policies of a country. The report of the 19th Communist Party of China National Congress proposed that promoting the formation of a new pattern of comprehensive openness, and employment is the biggest livelihood. It′s important to deal with the relationship between openness and employment. The strategy of "Made in China 2025" proposes to achieve the goal of manufacturing transforming and upgrading through three steps. Therefore, how to accelerate industry upgrading, how to guarantee the employment of ordinary people and ensure the interests of different groups when promoting the opening up become a major issue which needs urgent consideration. 
     This paper employs the firm level data of the business environment surveys of 26 countries in Central and Eastern Europe and Central Asia, BACI data, WITS data and World Development Indicators to examine the impact of trade liberalization on the skill structure of firm employment. In summary, the following conclusions can be drawn: First, trade liberalization will promote companies to hire a higher proportion of high-skilled labor, which is robust when using alternative measurement of trade liberalization and the skill structure of firm employment, and also when solving the potential endogenous problem by using the method of instrumental variable. Second, the mechanism analysis shows that trade liberalization will lead to fierce competition and industry upgrading, which will strengthen the preference for high-skilled labor. Third, heterogeneous analysis indicates that the baseline result of trade liberalization promoting higher proportion of high-skilled labor is more obvious for medium-productivity firms, small firms, domestic firms, single-product firms and firms in developed countries and firms in skill abundant countries. The conclusion of this paper implies that trade liberalization will bring about upgrading of the skill structure of firm employment and promoting the efficiency of the labor market allocation, which gives a new way for trade liberalization to improve the national welfare.
    There are significant policy implications. On the one hand, the result of this paper is in line with the interests of enterprise and country, and trade liberalization encourages economy upgrading. On the other hand, there should be noticed that the problem of structural unemployment may be severer, plenty of high-skilled labor are employed, resulting in the low-skilled labor nowhere to settle down. To this end, the following policies can be put forward. First, government and enterprises need to pay more attention about education, research and development, cultivate more high-skilled labor, provide backup labor force for firms; promote the development of high-tech and knowledge-intensive industries, reduce the dependence on labor to cope with the shortage of labor force. Second, government and enterprises can strengthen the training of the existing low-skilled labor to improve their working skill, promote the transformation of non-skilled labor to skilled labor, and solve the employment of low-skilled groups. Third, government should support the development of private enterprises and small-sized and medium-sized enterprises, promote transformation and upgrading of these firms, play their role in employment absorption. Finally, government should actively promote the "Belt and Road" initiative because it plays an important role in the adjustment of economic structure and allocation of resources for countries along the line.
    This paper makes following contributions. First of all, this article directly examines the impact of trade liberalization policy on the skill structure of firm employment, which is rare in the existing research. Secondly, this paper adopts the firm level data of the business environment survey of 26 countries released by the World Bank, covering countries of multi-level economic development. Compared with using the data of only one country or country with a specific development level, our conclusion is more general and applicable. Thirdly, this paper refers the method of Crozet et al. (2018) to solve the potential endogenous problem. Last but not the least, this paper proposes and tests two channels of how trade liberalization leading to changes in the skill structure of firm employment, and analyzes the mechanism behind the phenomenon. In addition, the paper also examines the heterogeneous impact of the trade liberalization on different types of firms, and has obtained some interesting conclusions.