With the constant increase in China’s stock pledge transactions, controlling shareholders’ equity pledges may result in inadequate investment, which government regulatory authorities, investors, and financial management departments should be aware of. Taking China’s A-share listed companies from 2013 to 2019 as a sample, this paper examines the impact of controlling shareholder pledge on equity capital cost. It is found that the equity capital cost of listed companies increases significantly after controlling shareholder pledge, and high-quality audit reports help reduce the influence of controlling shareholder pledge on it. In addition, the mechanism test shows that controlling shareholder pledge impacts the equity capital cost by reducing stock liquidity and increasing the tunneling behavior of large shareholders. Further research shows that under controlling shareholder pledges, improving the quality of information disclosure can help reduce the equity capital cost, while stock price risk can increase the equity capital cost.