Abstract: Enhancer of growth of microcapsule-type recombinant common carp (Cyprinus carpio) growth hormone (rcGH) was investigated with the sandwich enzyme-linked immunosorbent assay (ELISA) for Chinese grass carp (Ctenopharyngodon idellus) growth hormone and enzyme-linked immunosorbent receptor assay (ELISA-RA) for fish.The pH threshold values of dissolution at ratesin Ⅰ and Ⅱ were 6.0 and 6.6,respectively.At pHs above threshold value,the releasing rate of rcGH from microcapsule Ⅰand Ⅱ increased gradually as pH values increased and time went on.Following feeding of microcapsule Ⅰcontaining rcGH or rcGH (1 mg rcGH/g food pellets) to Clarias batrachus,serum rcGH levels of the former started to elevate after 15 h,reaching a maximum after 24 h,and undetected at the 48 h after administration,whereas rcGH in serum of the latter was undetected from 6 to 60 h.It is quite clear that microcapsuleⅠplays a role in protecting rcGH againt degrading by the proteinase in the digestive tract to some extent and microcapsuleⅠand Ⅱ possess the characteristics and function of antacid capsule.