Abstract: Laboratory experiments were conducted with P. lethostigma juvenlies (total length 10.1) 40.9mm) in different treatments The results showed that Cannibalism occurred more frequently in hetreogeneous than in homogeneous size groups, the cannibal behavior at insufficient diet were marked higher than those at full diet, the stocking density had influence on the cannibal behavior of the young fish and the cannibal rate at high density was higher than at low density. (1) It suggested that the differences in body sizes was a main reason causing the cannibalism among the young fishes, and when the young fishes were insuff-i cient diet in the group of (10.1 ± 0.4)) (20.3 ± 0.3) mm, the rate of cannibalistic death was 53%1(2) Hungry had influence on the cannibal behavior of P. lethostigma young fishes which were hungry after 24h, and the rate of cannibalistic death was 20% in the group of 15.0± 0.4mm1(3) The kind of diet and the turbidity of water had no significant effect on cannibalism, when the stocking density was 20/L, the rate of cannibalistic death was 5% in the group of turbidity of water, and in the other was 8%.