Long-chain polyunsaturated fatty acids (LC-PUFA) are essential fatty acids (EFA) and have important roles in growth, development and physiological function of fish. Fish oil is characterized by high content of n-3 LC-PUFA, but harvesting fish oil is controversial due to limited wild fish stock and increased production cost. Silver pomfret (Pampus argenteus) is an important economic species in coastal areas of China. There are many problems in the technological development of artificial breeding and aquaculture for silver pomfret. For the purpose of researching and developing artificial feed, reducing feed cost, improving fish health and survival rate, in this study, 4 experimental dietary groups were designed for the feeding trial: 100% fish oil (FO), 70% fish oil and 30% soybean oil (FSO), 30% fish oil and 70% soybean oil (SFO), and 100% soybean oil (SO). To explore the effect of substitution of dietary fish oil by soybean oil on silver pomfret, serum lysozyme (LZM) activity and tissue antioxidant capacity were measured. The results suggested that serum LZM activities were the highest in SFO group, and the lowest in SO group, although no significant difference was detected (P>0.05). Muscle malondialdehyde (MDA) contents of FSO and SFO group were significantly higher than that of FO and SO group (P<0.05). Liver MDA contents in FO and FSO groups were significantly higher than that of any other groups (P<0.05). The highest superoxide dismutase (SOD) and catalase (CAT) activities of serum and muscle were in SFO group. By contrast, SO group had lower SOD and CAT activities than any other groups. The liver SOD and CAT activities were found significantly higher in FO group than other groups (P<0.05). T-AOC of muscle and liver in FO and FSO were higher than other groups, and group SO had the highest serum T-AOC. This experiment suggested that replacing dietary fish oil by soybean oil for 30% or 70% can promote immune and antioxidant function of juvenile silver pomfret. But replacing dietary fish oil by 100% soybean oil had negative effect on immunity and growth of silver pomfret.