A heat pump low-temperature circulating grain dryer control system was designed for the low-temperature circulating grain dryer using air source heat pump as the heat source. A multi-mode soft logic system was employed to control the low-temperature circulating grain dryer and heat pump system. In the hierarchical system, the PLC was used as the control core and touch screen as the man-machine interface, programming through the sequential function chart (SFC) and ladder diagram, which guaranteed the multi-mode operation of heat pump low-temperature circulation grain dryer and supported manual adjustment and setting of drying parameters, realtime monitoring of grain moisture content and drying temperature and other functions. The experiments validated the operation of the dryer in manual mode, automatic mode and timing mode. The designed logic control system had advantages of high degree of automation, good stability and high safety and so on. Additionally, experiment results on the control of the drying temperature showed that the mean error of the heat pump outlet temperature was 0.95℃ and the standard deviation was 0.93℃ at different ambient temperatures, which meant the control system had high accuracy and stability. The grain temperature was stable at about 33℃, which satisfied the operating requirements of the low-temperature circulating grain dryer.