Poecilobdetla manillensis were divided into different groups with dissimilar number in the wet rice field soil and kept hibernating at room temperature. The results showed that the survival rates decreased along with the increase of the number in different groups. When the number of P. manillensis over 1 800 leech per square meter, the survival rate decreased significantly. However, it wasn't different from the rate of the group which number was below 1500 leech per square meter (P > 0.05). The net weight of various groups decreased about 10.4%-15.6% respectively after hibernation and there was no significant difference among groups (P > 0.05). It is concluded that rice field soil is suitable for the hibernation of P. manillensis.