Mismatch is a critical consideration in analog circuit design. Knowledge of mismatch locations and an understanding of their impact on circuit performance are crucial for design optimization and process improvement. We present a circuit level mismatch diagnosis methodology in this paper. The functional parameters with abnormal values are measured as manifestations of mismatch, from which reverse tracing is employed to determine the mismatch source. The methodology is implemented on a representative benchmark and its efficiency confirmed by simulation results.