Fish schools present perfect order in dimension,which has attracted interest and attention of scientists.For observation of the structure characteristics of fish school,two video cameras were set up in lab to record the position of fish(Pseudorasbora parva)from up and side directions of aquarium simultaneously.Three-dimensional location data of each individual can be abstracted from the record in time series.The characteristic parameters data,nearest neighbor distance(NND),vision angle(VA),turning angle as well as individual swimming speed,have been analyzed for presenting the structure characteristics of fish school.The results show that NNDs of individuals have kept in a range of 0.5-2 BL mostly,and the preferred nearest neighbour distances(PNND)are 0.6-0.8 BL.To avoid a collision,the individual fish always keeps the neighbour fish located its visual field in range 80° and the variation of turning angle keeps the range from 0° to 30°(95.83%).Under natural conditions without any stimulus or disturbance,the fish swims at around 0.75 BL/s to match the others maintaining in schooling.The results of our study confirm that visual ability plays an important role in the schooling performance of P.parva,and the group structure is also affected by individual status(satiation and hunger).