To solve the problems of large space, low transmission efficiency, high maintenance frequency in existing coal mine belt conveyor transmission system, a kind of direct drive structure using outer-rotor Permanent Magnet Synchronous Motor (outer-rotor PMSM) was proposed, and a model-free adaptive control with cascade structure was applied to the speed control system of belt conveyor. According to the requirements of mine belt conveyor running, the detailed design parameters and mathematical model of this motor were given, and the ideal speed curves of starting and the steady state were set. By using model-free adaptive control algorithm, a cascade model-free adaptive control law was designed, and the cascade control system structure was also given. The simulation of the ideal starting curve in direct-drive system in coal mine belt conveyor for outer-rotor PMSM was conducted using Matlab software. The results show that the cascade model-free adaptive control algorithm reduces the speed tracking error and improves control precision, which suppresses the system noise and the disturbance for load changing effectively. This method achieves good startup and steady-state characteristics of belt conveyor.