The purpose of this study is to identify the determinants of actual share repurchased subsequent to an open market repurchase program announcements. According to related studies, I identify 11 variables that may impact actual share repurchased and use TOBIT and OLS regression model to examine the hypothesis. The empirical results show that share repurchases are negatively related to the company size and the stock return, but positively related to the pledged share of directors. In addition, if the stock price of the announcing company has exceeded the treasury stock repurchase price ceiling, it will reduce the company's ability to buy back shares.