In order to protect the privacy of short message, a privacy protection scheme for short message is proposed in this paper, which is based on asymmetric encryption. In this security system, the message is first encrypted by the receiver's public key to obtain message ciphertext. Then the message ciphertext is combined with the life time information and encapsulated into Message Self-destructing Object(MSO). At last, the MSO is sent to the receiver through the operator. After getting the MSO, the receiver can use the private key to decrypt the ciphertext to obtain the original message only when the current time is in its life time, and after its life period, the system will automatically delete the MSO to protect the user's privacy. The experiments show that this scheme can effectively protect the privacy of short message and remove the expired MSO. And the system has low performance overhead, it is suitable to be used widely in people's daily life.