SM2 digital signature algorithm (SM2-DSA) is the Chinese version of the elliptic curve digital signature algorithm (ECDSA), which has become one of the international standards of elliptic curve cryptography. Despite its solid theoretical security, SM2-DSA is still prone to a variety of physical attacks. Hence, it is important to research the security of the SM2-DSA implementation. In this paper, we propose a fault attack model for the SM2-DSA based on the weak elliptic curve. Experimental results show that the proposed model can directly calculate the parameters of the fault curve by using the fault signature pair, and if the fault injection location is correct, we only need an error signature pair to recover the 256-bit signature private key within 3 minutes. Compared with the general weak elliptic curve attack, our model is more practical and 20% more efficient in recovering the private key.