In recent years, stock pledge financing becomes an important kind of financing means of listed companies’ controlling shareholders. However, pledge financing can also increase the risk of losing control rights faced by controlling shareholders, as well as bring cash flow to them at the same time. Thus the controlling shareholders of listed companies may change their operational decisions to reduce this risk. The enterprise is the main body of economic growth, while innovation is the important source of the enterprise to improve productivity. Unlike capital investment, innovation investment faces a higher risk, which needs a long-term stable source of funding but comes a lower short-term return. Therefore, under the background of stock pledge, how do the controlling shareholders of listed companies treat the high-risk innovation investment? 　　Since the financial crisis, the frequent adjustment of monetary policies in our country leads to an uncertainty expectation, which exacerbates the instability of the stock market and worsens the financing environment of the enterprise. With the increase of monetary policy uncertainty, how does controlling shareholders’ stock pledge affect innovation? It is worth finding answers to such a question, which has a strong practical significance on creating a good innovation environment and maintaining the stability of the capital market.　　Leveraging a sample of A-share listed companies from 2005-2015, this paper investigates the relationship between controlling shareholders’ behavior and enterprise innovation, and the adjustment effect of monetary policy uncertainty. The results show that controlling shareholders’ stock pledge leads to a decrease in enterprise innovation, and this inhibiting effect will be sustained for a long time. Monetary policy uncertainty strengthens the negative relationship between stock pledge and enterprise innovation. Furthermore, compared with the strategic innovation, we find that controlling shareholders’ stock pledge has a stronger inhibitive effect on substantial innovation. Considering the mechanism of stock pledge on innovation, we find that risk-taking and financial constraints are two transmission channels between stock pledge and innovation.　　We advance the literature in several ways. First, we broaden the literature of controlling shareholders’ behavior on the economic consequence of enterprise investment and financing decisions. In addition, we enrich the mechanism of stock pledge on enterprise innovation. Based on the myopia theory and the agency theory, our research finds that there are two transmission channels between stock pledge and enterprise innovation: （1）After pledging the stock, controlling shareholders may force listed companies to avoid risky project for decreasing the volatility of stock price. Then the risk profile of listed companies decreases, resulting in a lower innovation level. （2）After pledging the stock, the agency conflict becomes stronger, which increases the financial constraints faced by listed companies, resulting in a lower innovation level. Second, we distinguish the different types of innovation to examine the different effects of stock pledge, which extends the literature of enterprise innovation. Third, we further examine the effect of the dynamic adjustment of monetary policies on the negative relationship between stock pledge and enterprise innovation, which contributes to the macroeconomic policy and enterprise behavior research.