Abstract: The water loss of fruits and vegetables in precooling is a mass transferring process affected by the heat transfer, it is important for reducing the weight loss of fruits and vegetables to analyze the affecting factors in forced air precooling. Combining with the integrate heat transferring equation of spherical fruits and vegetables, the coupling equation of heat and mass transfer of water loss was derived by analyzing the process of water loss of fruits and vegetables in precooling, including the factors of the parameters of fruits and vegetables and precooling conditions. The effects of the internal water diffusion coefficient, precooling air velocity and precooling air relative humidity on water loss were analyzed. The results show that the structure parameter is the key factor and the effect of the air velocity on the precooling time is significant. The water loss is mainly affected by the structure parameters of fruits and vegetables and decreases with the increase of air velocity. The result was verified by the experiment with apple, which had a similar result with the theoretical analysis.