R-tGH by i. p. injection, oral administration and mixed with food can increase RSGR and RLGR of grass carp (Ctenopharyngodon idellus) fingerling, The results may suggest that r-tGH had biological activity on the fingerling and could accelerate its growth. In the meanwhile,r-tGH may be absorbed intactly into blood circulation by digestive tract then can express biological activity itself in the fingerling. The increase of condition factors of the fingerling with r-tGH administration are higher than the control, which may suggest that r-tGH stimulated weight gain better than length increase on the fingerling. The food conversion efficiency and serum GH concentration of the fingerling with r-tGH administration are higher than the control. And these may be the reasons of the growth promotion of r-tGH on grass carp fingerling.