Abstract: For problem that it is easy to take place spontaneous combustion in conveying coal by use of conveyor belt, a design scheme of detection device of coal moisture on conveying belt was proposed, and design of hardware and software of the device were introduced. The device adopts microwave transmission method to get coal moisture content through measuring microwave power attenuation. The calibration experiment demonstrates that the device has advantages of low error and high measuring accuracy, which provides an effective method of measuring coal moisture on conveying belt.