This study was conducted to investigate the effects of different fish oil replacement levels on reproductive performance, egg diameter, individual egg wet weight and dry weight, proximate composition and fatty acid composition in the eggs produced by Chinese mitten crab (Eriocheir sinensis). Five isonitrogenous and isolipidic fattening diets were formulated by the blending vegetable oils(soybean oil: rapeseed oil = 1:1) to replace 0, 25%, 50%, 75% and 100% of fish oil(defined as feed 1#, 2#, 3#, 4# and 5#,respectively).Each experimental diet was fed to three replicates and each replicate consisted of 25 females and 25 males.After 60-day feeding, four females and two males from each replicate were randomly transferred into the brackish water tanks for the mating, and the reproductive performance and egg biochemical composition were further studied for the evaluation of effects of fish oil replacement. The results showed that: (1) Feed 3# treatment started to spawn only after 10 days of post-mating, while there were 15 days of post-mating for the other treatments; the final ovigerous rate was 100% for the treatments of feed 1#, feed 3# and feed 5#, while the final ovigerous rate of feed 2# and feed 4# was around 80%; although feed 4# treatment had the highest egg production, fecundity and reproductive effort among five treatments, no significant differences were found among the five treatments(P>0.05). (2) As for the egg quality, feed 1# had the slightly higher egg diameter than the others,but no significant differences were found on egg diameter, individual egg wet weight and dry weight among the five treatment (P>0.05). (3) As for the egg biochemical composition, no significant differences were found for the moisture, crude protein, crude lipid and fatty acid composition in the eggs among the five treatments (P >0.05); the percentages of 18:2n6, and the ratio of n-6 polyunsaturated fatty acids/n-3 polyunsaturated fatty acids (∑n-6PUFA/∑n-3PUFA) increased with increasing the replacement levels of dietary vegetable oils, while the decreasing trend was found on the percentage of 22:6n3 in the eggs. In conclusion, dietary fish oil replacement have no significant effect on reproductive performance, egg quality, proximate composition, and fatty acid composition of eggs for feeding E. sinensis at middle stage of gonadal development. Therefore, the appropriate replacement level of dietary fish oil is around 75% in consideration of egg production and fecundity.