Digital signature technology is an important way to ensure the safety of terminal application.But due to the limited computing resources and security constraints on the mobile terminal,the mobile terminal can not guarantee the security of the private key.This paper designs a safe and efficient solution based on the digital signature technology,combining mobile terminal with signature server.The key is distributed into two parts,one part is stored in the signature server and the other is distributed to mobile terminals,the signature must include the two parts.Through this identity-based threshold signature technology,we realize the secure mobile terminal digital signature in the case of signature key can't guarantee safety.