Abstract: Based on the 185 kW motor drive system, the transmission performance is studied about the double permanent magnet disc synchronous couplers without isolation sleeves applied in mine direct-drive motor systems. Firstly, the structure and working principle of the synchronous permanent magnet couplers are analyzed, and then the magnetic field simulation, permanent magnet installation force analysis and temperature field distribution calculation under overload operation state are carried out. The main results are as follows: the maximum transmission torque reaches 2 600 N·m by using the form of 10 pairs, which meets the requirements of the 185 kW motor drive system; the installation force of a single permanent magnet is less than 46 N, and the axial force of inner and outer sleeve of the permanent magnet rotor is 1 000 N, and the radial force is 320 N in the case of misalignment 1 mm, thus the specific tools are required for the installation; the maximum temperature of the permanent magnet is 114 ℃, and the overload coefficient is above 2.0, which meets the requirements of overload operation.