Signcryption is a method of cryptographic that combines both digital signature and public key encryption in one logical step. This paper analyzed the characteristics of mobile service and the special request of signcryption. Then one identity-based signcryption scheme using the bilinear pairing was presented. The proposed scheme is proved to be secured assuming the bilinear Diffle-Hellman problem is hard. This scheme combined the signcryption and certificateless public key cryptosystem, and it would be more efficient than existing signcryption schemes.