The invention discloses a hot air drying system. The drying system is characterized in that a drying device comprises a box body, a temperature sensor, a flow speed sensor and a conveyer belt; the conveyer belt penetrates through the box body; the temperature sensor comprises an inlet temperature sensor used for measuring the temperature of hot air entering the drying device; an air inlet pipeline temperature sensor is in data connection with a central controller; and the central controller automatically adjusts the rotation speed of a driving motor according to the measured temperature of hot air entering the drying device, so that the transmission speed of a belt pulley is adjusted, and the coal feed quantity of unit time is controlled. According to the hot air drying system, the inlet air temperature of the drying device and the rotation speed of the motor are connected for the first time, an intelligent control relationship of the inlet air temperature and the rotation speed is established, coal is intelligently dried through utilizing solar energy, the resources are saved, and the drying system is environment-friendly.