Abstract: The types of digestive enzymes were analyzed in digestive tracts of common carp Cyprinus carpio silver carp Hypophthalmichthys rnolitrix, bigheand carp A ristichthys mobilis, grass carp Ctenopharyngodon idellus by polyacrylamide gel electrophoresis, and the relative activities of the digestive enzymes were determined in the fishes by colorimetry and titration.The results showed that the order of the protease activity was arranged as common carp 〉silver carp 〉 bighead carp 〉 grass carp, and that for amylase activity as grass carp 〉 bighead carp 〉common carp 〉silver carp. The digestive enzyme expression in these fishes was found to be paralleled to the histology structure of digestive tracts. The maximal digestive enzymic activity was observed in the 2/5 parts in anterior end of the digestive tract （G1, G2）, where was found to be the main place for digestion in those stomachless fishes, followed by the following 1/5 part of digestive tract （G3）. The minimal digestive enzymic activity was occurred in the last 2/5 parts （G4, G5） of the intestines. The findings provide a theoretical basis for the nutritional physiology, the development of feedstuff and the management for germplasm in these fisheries.

Key words: Cyprinus carpio, Hypophthalmichthys molitrix, Ctenopharyngodon idellus, A ristichthys mob ilis, digestive tract, digestiveenzymes