Rousettus leschenaulti is a common fruit-eating bat in Xishuangbanna,Southwest China,its feeding behavior was observed in the field and its food intake on fruit of Dimocarpus longan was estimated in the laboratory. R. leschenaultia usually caught fruits from one tree and took the food to another species of trees to consume them in the study area. During the period of the research,we did not observe the bat consuming the fruit of D. longan in where they got them. There were three foraging peaks at 20:30 - 21:00,22:00 - 22:30 and 1:00 - 1:30 in the night from 19:30 to 5:30 next morning. . We fed the 10 bats with the fruits of D. longan and found that each bat consumed 6 to 20 fruits of D. longan depending on their body weight. The quantity of food took by each bat in one night was as weight as 1 - 1. 8 times of its body mass.