Abstract: The features of ‘three circles’ in the Humidicool System were first indicated in this paper. The principle about transfer of heat and mass in the mixed heat exchanger was analysed. The experiment on suitability of fresh agricultural products and detection of operating characteristics in the humidicool store were carried out. It shows that humidicool system has many advantages such as high effectiveness of compressors and low electricity cost.The condition in its room with high humidity and low temperature is suitable for fruits and vegetables to be precooled and kept fresh.