Abstract: The aims of the present study were to find out the digestive enzymes distribution features of each digestive organs in Silurus asotus as well as the optimum temperature and pH of digestive enzymes,and to elucidate the effects of temperature and pH on the nutrition requirements of Silurus asotus.The study would provide theoretical basis and ref-erence for studying digestive physiology and nutrition requirements of Silurus asotus.In the present study,the Silurus asotus in Dongting Lake area was chosen as research material.Effects of temperature and pH on the activities of three digestive enzymes(protease,lipase and amylase) in stomach,hepatopancreas,anterior intestine,middle intestine and posterior intestine of Silurus asotus were studied by means of enzyme analyses.The protease,lipase and amylase activ-ity of different digestive organs of Silurus asotus were determined by using Folin-phenol method,polyvinyl alcohol emulsion of olive oil hydrolysis method and 3,5-dinitrosalicylic acid method respectively.Then,the experimental data were analyzed for ANOVA and multiple comparisons(LSD method) using SPSS 13.0 software package for windows.The data were expressed as mean ±SD.The results showed that the activities of all digestive enzymes in Silurus asotus increased at first and then decreased with temperature and pH increasing in the designed temperature and pH ranges.In stomach,the optimal temperature for protease was 40℃,whereas all in hepatopancreas,anterior intestine,middle intes-tine and posterior intestine were 45℃,when the reaction pH value was 7.5.The optimum temperature for lipase in stomach,hepatopancreas,anterior intestine,middle intestine and posterior intestine were all at 35℃.The optimum temperature for amylase in stomach was 35℃.The others were all 35℃ respectively.The optimum pH in stomach,hepatopancreas,anterior intestine,middle intestine and posterior intestine were all 7.5 for lipase and 2.0,8.5,7.5,8.0,8.0 for protease respectively.The optimum pH in hepatopancreas for amylase was 7.5 and others were all 7.0.The re-sults indicated that amylase was conductive to weak acidic condition,and protease in hepatopancreas and intestine were conductive to weak alkaline condition,while the protease in stomach was conductive to acidic condition.The activities of digestive enzymes in Silurus asotus have organic specificity.Under optimum temperature,the activity of protease in different organs was in the order of anterior intestine hepatopancreas stomach middle intestine posterior intes-tine,and the activities of lipase were hepatopancreas stomach anterior intestine middle intestine posterior intes-tine,while the activity of amylase was hepatopancreas anterior intestine middle intestine posterior intestine stomach.Results showed by multiple comparisons that there were significant differences(P0.05) among different temperature or pH of the same digestive enzyme in the same place,and there were also significant differences(P0.05) of the same digestive enzyme among different digestive organs in the same temperature or pH.