In order to solve the problems of low efficiency and large start-up shock of the belt conveyor main roller which is driven by an asynchronous motor with a hydraulic coupling, a direct drive roller control scheme of belt conveyor based on an external rotor permanent magnet synchronous motor(PMSM) is proposed. In order to realize low-speed high-torque control, a vector control strategy based on the rotating coordinate system with zero direct axis current is used. In order to solve the problem of small counter-electromotive force and low accuracy of rotor position and speed estimation during low-speed operation, the high frequency pulse signal injection method is applied to estimate the rotor position and speed. The experimental platform of direct-drive roller speed control system is established to conduct steady-state characteristic test, start-up characteristic test and load characteristic test. It is verified that the PMSM direct-drive roller control system has fast torque response and stable adjustable speed in the speed range of 0-90 r/min, which can meet the start-up speed regulation requirements of low-spreed high-torque belt conveyor.