In this article, we propose an efficient statistical parameter extraction method to accurately model the random device mismatch of MOSFETs. The key idea is to approximate the performance variations as mathematical functions of device mismatch. Based on these approximated functions and the electrical test data, we solve the unknown statistical parameters by nonlinear optimization. Our numerical experiments demonstrate that the proposed method can remarkably improve the modeling accuracy with affordable computational cost, compared against the state-of-the-art techniques.