In order to find out how the structural space of artificial reefs influence fish behavior,we used the combination of different representative reefs to simulate the structural space of artificial reefs,under the different flowing velocity of 19.1,23.4,and 27.7 cm/s.This paper discussed how the different sizes of structural space influence the distribution of juvenile Sparus macrocephalus in tank,and summarized the range of loving flowing velocity of juvenile S.macrocephalus.The result shows that when the horizontal size of structural space is 38.8 cm,the juveniles S.macrocephalus have a highest tendency ratio to reefs(43.1%)compared with other cases,and the range of loving flowing velocity is 9.6-23.4 cm/s;when the vertical size of structural space is 20 cm,the juveniles S.macrocephalus have a highest tendency ratio to reefs(50.1%)compared with other cases,and the range of loving flowing velocity is 6.7-27.9 cm/s.On the whole,the horrizotal structural space has a higher effect of gathering fishes compared with the vertical structural space.