An motor torque fault diagnosis for four wheel independent motor-drive vehicle is presented in this paper. Focusing on the fault that the actual motor torques differ from the motor torques commanded by vehicle control unit, the fault parameters are introduced to represent the differences and a nonlinear vehicle dynamics model is built. This model considers vehicle body nonlinear dynamics, wheel dynamics, and tire nonlinear characteristics, and the fault parameters are set to be the coefficients of motor torque commands. Then the motor fault diagnosis problem is converted to these fault parameters identification problem, and unscented Kalman filter is implemented to identify them in real time. With the road test data of a four wheel independent motor-drive vehicle, the fault diagnosis method is testified to be effective both in normal and extreme handling situations.