Rapid development of wireless communication technology has greatly promoted the ubiquitousness of mobile devices. Mobile devices enable users to access Internet services anytime and anywhere. Because of the conjecture of the cyberspace, the digital signature is used as a kind of technique with the functionality of the integrity authentication, identification, and non-repudiation. However, mobile devices tend to be more easily lost or hijacked cause relatively weak protection on the private keys (the root of the digital signatures trust). To ensure the confidentiality of private keys, two-party signature is a viable method to avoid fraudulent key usage or key theft. Therefore, in this paper, we focus on the SM2 signature algorithm, which is standardized in GM/T 0003—2012“SM2 Elliptic Curve Public Key Cryptography”, and design a lightweight two-party SM2 signing protocol. Unlike standard secret sharing, a valid signature now is generated interactively between a client and a server, while the original key never being exposed. We mathematically prove the security of the proposed protocol. Findings from the performance evaluation of the protocol show that it achieves good performance, with a single signing operation taking 4.381ms for the client and being roughly equal to the original SM2 signature in the same testing environment.