The invention discloses a safe mail 
system based on a USBKEY (Universal Serial 
Bus Key) and a mail encrypting-decrypting method. The 
system mainly comprises a first mail 
system, a second mail system, a mail encrypting system and a mail decrypting system. When 
logging in the mail system, a user is required to insert a USBKEY disc (including a private key 
certificate) and input the 
password of a 
certificate, besides inputting the 
password of an account; and if the input 
password is wrong, the user is refused to log in the system. When a mail is transmitted, a COM (
Component Object Model) 
assembly calls a private key in the USBKEY disc to generate a Hash value, the mail is signed up by using the Hash value, and a public key of an addressee is called to encrypt the mail; and when the mail is looked up, the private key in the USBKEY disc is required to be called to decrypt a key to generate a Hash value by a browser COM 
assembly after the key of the addressee is obtained, the mail is decrypted and the signature of the mail is checked by using the Hash value, therefore, the mail is 
safer in the transmitting process, and the authenticity of the mail is also ensured.