Abstract: With the rapid development and popularization of electronic commerce, the secure payment in the area has become more and more important and is a key technology that impacts on the development of ccommerce. Aiming at the standard Secure Electronic Transaction protocol (SET) , some improvements were done for the SET protocol in order to assure the goods atomicity and certified delivery. Then, this paper proposed a secure e-commerce payment system based on the four parties that can not only support the goods atomicity and certified delivery, but also access the key electronicevidence automatically and deal with the transaction disputes. In the meantime, the formal description of the protocol is presented. Finally, the security of the proposed protocol was compared and analyzed.

Key words: E-commerce payment, Goods atomicity, Confirmation delivery, Secure electronic transaction