Based on the sample of listed companies in China which have announced open market share repurchase in year 2005 to 2022, this paper examines the changes in the cost of capital after share repurchase. We find that the share repurchases significantly improve the cost of capital. Particularly, the improvement on cost of capital is more obvious for the companies with high financial risks. Further research also shows that companies with high financial risk have worse long-term market reactions after announcements of share repurchase. The article explains the lack of long-term value of share repurchase in China currently, from the perspective of the cost of capital, revealing that the long-term effect of share repurchase is subject to the internal conditions of companies.