An 8-week feeding experiment was conducted to investigate the effects of lysine on growth performance, body composition, digestive ability and determine the quantitative lysine requirement of juvenile black sea bream (Sparus macrocephalus). Three hundred and sixty fish with initial body weight of (9.13±0.09) g were randomly divided into 6 treatments with 3 replicates each and 20 fish in each replicate.Six treatments were fed with 6 isonitrogenous and isoenergetic diets containing 6 levels of lysine (2.08%, 2.52%, 2.88%, 3.25%, 3.68% and 4.05%). The results showed that, weight gain ratio (WGR) and specific growth rate (SGR) increased with the level of dietary lysine increased to 3.25% from 2.08%(P<0.05) and both showed a declining tendency thereafter. Feed efficiency (FE) was lower for fish fed with the lower lysine level(2.08% and 2.52%) diets (P<0.05) and it showed no significant differences among other treatments (P>0.05). The protein efficiency ratio (PER) increased significantly with the level of dietary lysine increased to 3.25% from 208% (P<0.05), and thereafter, it remained stable. Survival ratio (SR) and hepatopancreas index (HSI) had no relationship with the level of lysine. The whole body crude protein and crude lipid contents were significantly affected (P<0.05) by dietary lysine level, while moisture and ash contents showed no significant differences (P>0.05). Both total essential amino acid and lysine contents in liver obtained the highest values when the fish were fed with 3.68% lysine diet (P<0.05). The content of cholesterol (CHO), alanine transaminase (ALT) and aspartate aminotransferase (AST) in serum showed declining tendency with the increasing lysine level, and all reached the lowest values at 3.68% lysine level, however, no significant difference (P>0.05) was found in serum triacylglycerol (TG). The dry matter apparent digestibility (DMAD), crude protein apparent digestibility (CPAD) and fat apparent digestibility (EEAD) reached the highest values when fish were fed with 3.25%, 3.25% and 3.68% lysine diet, respectively. The results showed that the activity of protease in stomach, foregut and midgut increased with increasing lysine level although there was declining for fish fed with the last two lysine levels. The activity of lipase showed the reversed tendency. However, the activity of amylase was not influenced by lysine levels (P>0.05). Analysis of dose (lysine level)response (weight gain rate) with second order polynomial regression suggested that the lysine requirement of juvenile black sea bream was 3.28% of diet or 8.63% of dietary protein (DM basis).