A 12-week experiment was conducted to evaluate the effects of dietary soy lecithin on ovary development, gonadal histology and vitellogenin mRNA expression of swimming crab. 2×2 double-factor random block design was used to arrange 0% or 4% soy lecithin for mated or unmated female swimming crab, respectively. The results indicated that crabs fed the diets containing 4% soy lecithin had significantly higher gonadosomatic index (GSI), oocyte diameter, the levels of serum vitellogenin and sex steroids than those fed the unsupplemented with soy lecithin diets. Hepatopancreatic vitellogenin mRNA expression increasesed with dietary soy lecithin increasing from 0% to 4%. The results of hepatosomatic index (HSI) showed a reverse trend with GSI. Mated female crabs exhibited higher hepatopancreatic vitellogenin mRNA expression than unmated female crabs. Furthermore, the mated female crabs had higher ovarian yolk granules in number and size than those unmated female crabs. Mating treatment did not affect HSI, serum vitellogenin (VG) and progesterone (PG) contents. The interaction of dietary soy lecithin and mating on serum progesterone (PG) and estradiol (E₂) contents was identified. In conclusion, the dietary soy lecithin and mating stimulated had a positive effect on ovarian development in swimming crab broodstock, and mating stimulated had a more beneficial effect on promoting oocyte maturation.