国有股权对企业经营绩效的影响受到了广泛关注。使用2011—2021年A股上市公司数据和双重差分模型，本文检验了国有注资对企业创新数量和质量的影响。研究发现，总体而言，国有注资仅会提高企业的创新数量，但对创新质量没有影响。不过，当国有资本处于相对控股地位时，国有注资不仅能够提高创新数量，也能提升创新质量。而且，对初始创新水平低的企业，国有注资对创新数量的促进作用更为明显。机制分析表明，国有注资对企业创新数量的积极影响主要是通过帮助企业缓解融资约束、吸引高素质人才和提高企业创新意愿等方式实现的。本研究不仅从创新质量的视角拓展了有关国有注资经济效应的文献，还对发展混合所有制经济具有一定的政策启示。

With the progress of a new round of state-owned enterprise (SOE) reform in recent years, many SOEs have introduced non-state capital to implement mixed-ownership reforms. At the same time, state capital has been injected into non-SOEs in various ways. In this context, some studies have examined the impact of state capital injection (SCI) on firm performance, such as total factor productivity, profit margins, and operating income. In addition, limited literature has examined the influence of SCI on firm innovation, especially from the perspective of innovation quality. On the one hand, SCI may help firms acquire the necessary resources for innovation. On the other hand, it could potentially reduce the innovation efficiency and innovativeness of a firm. Therefore, further theoretical analyses and empirical tests are needed to explore the impact of SCI on firm innovation. Consequently, we investigated the impact of SCI on the quantity and quality of firm innovation and the potential underlying mechanisms. This research has not only contributed to the literature on the economic implications of SCI but also provided some policy insights for the development of a mixed-ownership economy.By employing a staggered difference-in-differences research design and utilizing the data on A-share listed firms from 2011 to 2021, we found that SCI generally only facilitates an increase in the quantity of firm innovation without having a significant impact on the quality of firm innovation. However, when state capital becomes the relatively controlling shareholder, SCI increases not only the quantity but also the quality of firm innovation. Moreover, SCI has a more pronounced effect in promoting the quantity of innovation for firms with a lower initial level of innovation. The mechanism analysis suggests that the positive impact of SCI on firm innovation quantity is mainly due to the alleviation of financing constraints, the attraction of high talent, and the enhancement in the willingness of firms to innovate, rather than an increase in opportunities for joint research and development.The contributions we have made in this paper are threefold. First, we have extended the literature on the economic effects of SCI and mixed ownership reforms by examining the impact of SCI on firm innovation, particularly on innovation quality, and provided new empirical evidence on the controversy surrounding the relationship between state equity and firm innovation. Second, we found that SCI does not increase the quantity of firm innovation by affecting the ability of firms to engage in joint research and development but rather by alleviating financing constraints, attracting high talent, and increasing the willingness of firms to innovate. Thus, the mechanism of the impact of SCI on firm innovation is revealed. Finally, this study conducted a heterogeneous analysis from the perspective of the relative control of state capital and the initial innovation level of firms, which will deepen the understanding of the relationship between SCI and firm innovation, and provide some policy insights for the layout optimization and efficiency improvement of state capital.The conclusions of our study have practical implications. For policymakers, first, they should continue to push forward the reform of state equity investment companies, utilize the role of state equity as an incubator for industrial funds, and support firms in key and difficult areas of the national economy to achieve technological breakthroughs. Second, the share of state equity in enterprises that have accepted SCI can be appropriately increased or even made to be controlled by the state, if necessary. Third, equity investment by state capital should prioritize areas that are under-innovated due to a lack of innovative resources. Fourth, the quality of innovation should be included as a criterion for evaluating the performance of managers of SOEs and state capital, which provides incentives for firms to pay more attention to the quality of innovation. For managers, first, for firms lacking resources for innovation, state capital and its links with the government should be utilized to obtain the resources needed to carry out high-quality innovation activities. Second, after the implementation of SCI, firms with a lower level of innovation should proactively pursue collaboration with SOEs and government-affiliated universities and scientific research institutions to enhance their capacity and potential for conducting high-quality innovation.