The love for Internet has been spreading all over the world in the recent years. Since Internet been used for business in 1991, lots of entrepreneurs or businessmen cannot but put themselves into the Internet competition for its attractive lower-cost commercial environments and its huge on-line customers. E-commerce （short for Electronic Commerce） is no doubt growing wider and faster because of their enormous and continuing investments. For customers, the ternet makes shopping be a piece of cake; as for the enterprises, it makes the commercial information sharing much easier and clearer over the electronic data interchange technology. The next step for E-commerce is build up an electronic government, an electronic bank, etc. Owing to its fast development, the ecurity of each transaction over Internet is becoming more and more important. The security, privacy, and integrity of transactions are the discussed points for the E-commercial environments. The identification for both sides in a transaction is discussed, too. In 1996, the first two CreditCard-issuing companies VISA and MasterCard proposed Secure Electronic Transactions, SET, which established a common and safe specification for the electronic business transactions. In this paper, we would like not only to introduce the types and structures of e-commerce, but also to tender all the possible secure threats it could meet; moreover, we will discuss the information secure technology. In the final, we will depict all the current protocols for the security on electronic business transactions, and the structure of SET as well.