To increase the torque capacity, the torque-transferring formula was deduced from electromagnetic force theory of virtual displacement according to working mechanism of magnetic particle clutch. The FEM model was established based on theory of Maxwell equation for analysis magnetic field and its simulation results conformed to the test results. According to the simulation results, improved design was made on magnetic particle clutch. The results showed that the improved magnetic particle clutch had a remarkable effect on the torque performance, and its torque performance increased by 45%.