150 shrimp(Fenneropenaeus chinensis) were sampled from the same culture pond with different sizes and the total haemocyte counts(THCs),muscular SOD activity and lysozyme activity of the shrimp were studied.There is no significant interrelationship between lysozyme activity and body length or body weight,nor between THCs and body length or body weight respectively when the shrimp size scattered in the range from 5.5 cm to 11.3 cm or(1.822 g) to 17.555 g.But the muscular SOD activity of the shrimp is positively interrelated with body length and body weight with a coefficient(r) of 0.559 and 0.436 respectively.