The infection rate of Oncomelania snails, emergence rate of Schistosoma japa-nicum cercariae, number of emerged cercariae and survival time of infected snails were observed experimentally by exposing single snails to different number of miracidia (i.e. 1, 5, 10, 20 and 40 respectively). The infection rate of snails was shown to be increased with the increasing number of miracidia. The frequency of cercaria emergence of infected snails varied significantly in different seasons and the highest was in spring and summer. No cercaria emergence was observed in winter. The average number of cercariae emerged from a single infected snail in each observation was 70.67, and through the whole lifetime in this experiment, 1,148.85?96.29. There was no significant difference in average number of emerged cercariae among the 5 groups of infected snails. The maximum number of cercariae emerged from one infected snail was 8,079. Calculated from the begining of cercaria emergence, the survival time of infected snails was in average 118.28?9.94 days, and the longest being 839 days. There was no significant difference in survival time among the 5 groups, and 94.8% infected snails died within one year.