Abstract: Drying materials is an energy consumed process, which sometimes brings pollution to environment, therefore, it is necessary to use solar energy for material drying, which is clean and low cost. However, solar energy is intermittent, this makes heat storage materials involved in solar drying. Paraffin was taken as the phase change material in this paper to study the characters of paraffin units during drying process, the results showed that there was temperature difference between outside and inner paraffin tube. The wall temperature, which related to the air velocity, decreased more quickly along with the increase of air speed. Through simulating the heat transferring inner paraffin tubes, the theoretic expression of paraffin solidification radius (rx) was got, by which the theoretic values of heat release time were also got, the results indicated that though the theoretic values were higher than that of the practical, the errors were less than 5%, which showed that these two sets of values were correspond to each other. Thus, this theoretic heat release equation could be used to predict the heat release time during material drying, which could not only avoid wasting energy stored by paraffin because of the limited time, but also avoid wasting time.