In order to optimize the structure and magnetic field distribution of the cylinder-disc type magnetorheological transmission device,taking the transfer maximum torque as the optimization design target,the optimization scheme of magnetic field distribution,effective working gap of magnetorheological fluid and transmission size were proposed.Based on the transmission characteristics of magnetorheological fluid,the optimal effective thickness of magnetorheological fluid working gap,the coil arrangement scheme with the best magnetic field performance,and the optimal design of the structural dimensions of the magnetorheological transmission were obtained,respectively,by using the finite element method and the control variable method.The results show that the coils arranged on both sides of the cylinder end face can significantly enhance the magnetic field strength and effectively improve the transmission performance of the magnetorheological transmission device.When the structure size of the magnetorheological fluid working gap meets the length ratio ε =1.6,the transmission torque reaches the maximum value of 13.3 N·m,and the transmission performance is the best and the device structure is compact.