A system for realizing digital certificate authentication and sensitive data encryption comprises: a client computer which is provided with a USB standard interface and can access the Internet; an electronic key which is controlled by a user and stores a chip containing the unique authentication digital certificate of the user; and a certificate identification server which is used for identifying the validity of the certificate and can communicate with the client computer and an application server by the Internet; wherein, the electronic key is accessed with the client computer by the USB interface. The system is safe, reliable, practical and convenient, and can meet the security requirements of commercial application data.