Abstract: Using Peru fishmeal as the only dietary protein source, the effects of dietary protein level (21.5%，32.2%，42.5% and 51.6%) on the growth, digestive enzyme activity and insulin-like growth factors-Ⅰas well asIGF-ⅠmRNA expression level of mud carp (Cirrhinus molitorella) were investigated by using 4 formulations. After an 8-week growth trial under different dietary protein levels, the protease activity showed a very significantcorrelation to specific growth rate (P0.01); the quantity of GH and IGF-ⅠmRNA in liver of mud carp showed a verysignificant correlation to specific growth rate (P0.01); the quantity of IGF-ⅠmRNA expression in liver of mud carp showed a verysignificant correlation to the protease activity (P0.01). The results indicated that IGF-ⅠmRNA expression level in liver was a suitable index for assessing the potential of new diets quickly.