Abstract: OpenSSL is a powerful secure open library for secure communication,and it has excellent cross-platform performance.SETprotocol is used to guarantee the security of the credit card-based payment system over Internet;it can show the detailed relationship among the parties in secure electronic payment exactly.In this paper,we mainly described how to use OpenSSLin windows to develop CA,where CAis a main part of a secure electronic commerce system,and then we apply it into SETprotocol to realize the function of CA.