This paper studies the effects of the buy-it-now price, seller's reputation, marketing association and the customer protection plan on the amount of transactions using data from Taobao.com. The empirical results show that the price has a significant negative impact on the sale, and seller's good reputation has a positive impact on the sale. However whether in the marketing association or not doesn't affect the sale significantly, but sellers who join the customer protection plan can get more sales. The results indicate that the reputation system has impact on online transaction, but the impact is influenced by many factors including Taobao's policy.