Existing research mainly examines the differences in performances of different stores, affiliated to different sellers and from the same e-commerce platform, which is defined as seller performance difference within e-commerce platform. However, few scholars pay attention to the differences in performances of different stores, affiliated to the same seller and from different e-commerce platforms, which is defined as seller performance difference between e-commerce platforms. Hence, this paper explores the effect and mechanism of e-commerce platform reputation on seller performance via three studies on the basis of reputation theory, in order to find an explanation to the seller's performance differences on different e-commerce platforms.The findings indicate that e-commerce platform reputation has a significantly positive effect on sales, but has no significant effect on price.Moreover, e-commerce platform reputation affects sales primarily through lock-in effect and signaling effect, and the impact is more beneficial when the product is an unpopular product than when it is a popular product. The lock-in effect of e-commerce platform reputation is mainly demoristrcfed by the fact that e-commerce platform reputation has a positive effect on buyers' loyalty to the e-commerce platform exclusively through product variety and seller expertise. In addition, the more experienes the buyers have in transactions on e-commerce platform, the stronger the seller expertise plays intermediary role to e-commerce platform reputation and buyers' loyalty to the e-commerce platform, but buyers’ experience has no moderating effect on the mediating role of product variety. The signaling effect of e-commerce platform reputation is mainly demonstrated by the fact that e-commerce platform reputation has a positive effect on purchase intention exclusively through perceived product quality. Furthermore, the mediating effect of perceived quality is significant for search products, while not significant for experience products.