Abstract: According to process requirements of rice drying, taking air source heat pump grain dryer of a family farm in Taizhou City as an example, performance of air source heat pump hot air unit based on internet of things was tested and studied under different ambient temperatures and matching different dryer conditions．Data such as temperature, air volume and power consumption of hot air dryer were collected．Actual performance of heat pump system was analyzed by calculating data of heat production, coefficient of performance（COP）, specific moisture extraction rate（SMER）and drying cost．Results showed that performance of air source heat pump system was significantly affected by average ambient temperature．With increase of ambient temperature, heat produced by heat pump gradually decreased, COP increased and SMER increased．However, when ambient temperature was lower than 9 °C, outlet air temperature of heat pump could not reach set value, COP and SMER were lower than mean value．The system performed well when ambient temperature was higher than 9 °C．