This paper selects listed companies in Shanghai and Shenzhen A stock markets from 2008 to 2016 as research samples and start empirical study of the impact of corporate social responsibility on corporate cash dividend distribution at first. The results of this study show that companies with better social responsibility performance tend to distribute or continuously distribute cash dividends, and have the higher the cash dividend payout rate. Next, this paper studies the impact of corporate cash dividends on corporate investment efficiency. Research shows that on the one hand, the company with surplus free cash flow can suppress agency problem by distributing cash dividends to reduce the free cash flow of the company, then alleviate the over-investment in such company. On the other hand, the positive signals sent to the market by continuous distribution of cash dividends have brought new financing to the company, alleviating under-investment by companies with limited free cash flow. Finally, this paper further studies the role of corporate social responsibility in the correlation between cash dividends and investment efficiency. The results show that companies can increase the cash dividends by fulfilling their social responsibilities, which can significantly increase the extent to which cash dividends can alleviate over-investment. Companies that fulfill their social responsibilities are more likely to distribute cash dividends continuously, thereby increasing the mitigation of under-investment.