Recombinant silkworm (Bombyx mori) nuclear polyhedrosis viruses were applied to express recombinant grass carp growth hormone (r-gGH), which shows similar immunoactivity and bioactivity as natural grass carp growth hormone (GH). To save lots of effort in the downstream work, especially to get rid of the complicated purification of r-gGH, the silkworms expressing r-gGH we used as a foodstuff additive with aims to stimulate growth of juvenile grass carp (Ctenopharyngodon idellus) and to optimize administration conditions for further economic and practical applications in largescaled aquaculture. Silkworms expressing r-gGH were freezedried, ground into powder, mixed with basic foodstuff, and then orally administered to cultured juvenile grass carps in Zhongshan University,Guangzhou. The dietary delivery experiments proved that r-gGH can be absorbed into the circulation and transported to target organs to play its physiological roles. Short-term feeding of r-gGH silkwormcontaining foodstuff (r-gGH scf), compared with feeding of normal silkwormcontaining foodstuff or basic foodstuff, significantly elevated serum GH levels in juvenile fish at 2 h and 6 h post-feeding. Feeding everyday or every 3 days also increased fish serum GH levels, and remarkably improved fish growth. Applying different doses of r-gGH silkworms, 10 or 20 mg·g^-1 diet, caused significant elevation of fish serum GH levels during short (3 days) and long (42 days) treatments. Longterm feeding (for 42 days) of r-gGH scf demonstrated remarkable stimulation on fish growth, with significant increases in relative size growth rate, relative length growth rate, food change efficiency and condition factor. In a word, our studies demonstrated that dietary delivery of r-gGH in r-gGH scf showed GH immunoactivity and bioactivity in cultured juvenile fish; and subsequently resulted in dosedependent increase in fish serum GH level, and stimulation on fish growth. Our work suggests that oral administration of recombinant GHcontaining silkworms in diet is a promising way to accelerate growth rate of cultured fishes in future aquaculture.