An 8-week feeding trial was conducted to study the effect of dietary n-3/n-6 fatty acid ratios on growth performance, body composition and serum antioxidant capacity of oriental river prawn (Macrobrachium nipponense). Five isonitrogenous and isolipid diets with different n-3/n-6 fatty acid ratios (D1: 0.29, D2: 0.56, D3: 1.02, D4: 2.20, D5: 8.52) were formulated to feed five groups of shrimps, respectively. Each diets was fed 4 tanks (4 replicates) with 45 prawns per tank.The results showed as follows: the survival rate of M. nipponensis was not significantly affected by n-3/n-6 fatty acid ratio in diet. The WGR and SGR of the prawns increased first and then decreased with the increasing dietary fatty acid ratios, and the WGR and SGR in D3 group was the highest and significantly higher than those of D1 group. The dietary n-3/n-6 fatty acid ratio had significant influence on the crude fat (CF) and crude protein (CP) of the whole body, and the crude fat reached the maximum value in D4 group, which was significantly higher than those in other groups. The crude protein of whole body in D3 group was significantly higher than those in D2, D4 and D5 groups. The n-3/n-6 fatty acid ratio in muscle was significantly positively correlated with the dietary n-3/n-6 fatty acid ratio. The serum superoxide dismutase (SOD) in D5 group was the highest, which was significantly higher than those in groups D1, D2 and D3, and not significantly different from that in group D4. Glutathione peroxidase (GSH-Px) reached its highest in D3 group, significantly higher than those in other groups. Serum malondialdehyde (MDA) was the highest in D5 group, which was significantly higher than those in D1 and D3 groups. The Hsp60 expression was the highest in group D4 and significantly higher than that in group D5, but not significantly different from groups D1, D2 and D3. The highest expression levels of Hsp70 and Toll in D2 group were significantly higher than those in other groups. Myd88 expression was the highest in D5 group and significantly higher than those in other groups. In conclusion, the dietary n-3/n-6 fatty acid ratio 1.02-2.20 can significantly improve the growth performance and non-specific immunity of M. nipponensis, and change the normal components and fatty acid composition of the prawn whole body.