Abstract: In view of problems of long measuring time and big error existed in current coal content recognition methods of coal-rock mixture, a coal content recognition method of coal-rock mixture based on phase difference detection was proposed. Relationship between coal content of coal-rock mixture and capacitance was gotten through experiment, parameters of phase difference detection circuit were chosen reasonably, and relationship between phase difference and the coal content was analyzed through numerical simulation and circuit simulation. The results show that coal content is lower than the minimum coal content threshold of coal mining when phase difference is positive, and coal content is higher than the minimum coal content threshold of coal mining when phase difference is negative, which indicate whether coal content achieves the minimum coal content threshold of coal mining can be judged accurately through detecting positive or negative of phase difference.