Abstract: The study was aimed to determine the requirement level of dietary protein for ricefield eel (Monopterus albus). The experiment was divided into 7 groups, with 4 replicates in each group. Each replicate included 25 ricefield eels with an initial weight of (17.1±0.2) g. The ricefield eels were fed seven isoenergetic diets respectively for 60d containing different levels of crude protein (32.74%, 38.50%, 42.26%, 48.35%, 52.65%, 57.87% and 62.31%) with fish meal and casein as the main protein source. Then the production performance, protein retention rate, physiological and biochemical indexes were evaluated to determine the requirement level of dietary protein. The results showed that 1) with the increase of feed protein level, the feed conversion ratio was decreased and then increased, but the weight gain rate, specific growth rate, protein efficiency ratio and protein retention rate increased first and then decreased. The growth performance was the highest in 57.87% of dietary protein group, and the protein retention rate was the best in 52.65% of dietary protein group. 2) with the increase of dietary protein level, the BUN in ricefield eel serum increased, the activities of GPT and GOT in ricefield eel serum decreased and then remained unchanged, the contents of TC, TG, HDL-C, LDL-C and blood glucose decreased, and the MDA content in ricefield eel serum decreased first and then increased, which was the lowest in 52.65% of dietary protein level. 3) With the increase of dietary protein level, the protease activities in liver, stomach and intestine of ricefield eel increased significantly and then increased slowly, the lipase activity in liver decreased significantly and then decreased slowly, the lipase activities in stomach and intestinal showed no significant difference, and the amylase activities showed no significant difference in stomach which decreased significantly first and then decreased slowly in liver and intestinal. These results indicated that ricefield eels will increase the feeding to supplement the protein requirement with low level of dietary protein. While the level of dietary protein was too high, the oxidative stress increased, thus ricefield eels will reduce the protein intake by reducing food intake. With the regression analysis of weight gain rate, protein efficiency ratio, protein retention rate and feed conversion ratio, the appropriate requirement level of dietary protein for ricefield eels is 48.51%—52.60%.