Under the guidance of the national strategy of innovation-driven development， there have been a number of Ｒ＆D alliances among Chinese companies in recent years． Taking as the research object the companies of the ChiNext market that are both active in Ｒ＆D alliances and innovation activities， the paper analyzes the mechanism of Ｒ＆D alliances and their impact on innovation． Our results， derived from propensity score matching method and difference-in-differences regressions， show that Ｒ＆D alliances have a positive effect on technological innovations． Companies that have Ｒ＆D alliances are better than companies that have not measured in different indicators that reflect innovation capability: The patent， the invention， technological diversification and innovative breakthroughs metrics all show a positive and robust effect of a Ｒ＆D alliance on innovation capability． Moreover， Ｒ＆D alliances have a lagging effect on technological innovation which increases first and then decreases with time． In addition， the governance structure of the Ｒ＆D alliance has a moderating effect． Compared with joint ventures， non-joint ventures have a greater role in promoting innovation． This paper provides theoretical and empirical evidence for the synergies of Ｒ＆D alliances in Chinese companies， as well as meaningful policy implications for the government and firms to enhance innovation capability．