As a key method of the on-line shopping, electronic
payment ought to not only make the procedure convenient and
fast, but also ensure the security and confidentiality of the
partners in the transaction. Therefore, a more comprehensive
electronic trading model is required. SET model is the normal
safety electronic on-line payment modal based on credit
payment currently. Through the commonly used payment model,
this paper described the security character of SET modal, and
took the case of electronic purse, detailed the electronic payment
transaction procedure under SET model.