Abstract: Abstract: A study was conducted to evaluate the effects of non-starch polysaccharide (NSP) enzyme on growth and feed utilization of Japanese flounder (Paralichthys olivaceus). The NSP-enzyme pretreated soybean meal (SBM) was obtained by fermentation with Candida utilis. Four isonitrogenous and isocaloric diets were formulated. The control diet contained 68.0% fish meal (FM) as the main protein source, whereas 45% of FM protein was replaced by SBM protein in the SBM diets with 0 and 0.2% NSP-enzyme. The NSP-enzyme pretreated SBM diet was formulated in which NSP-enzyme pretreated SBM protein replaced 45% of FM protein. At the end of the feeding trial, the specific growth rate (SGR), feed efficiency ratio (FER), protein efficiency ratio (PER) and nitrogen retention of fish fed the SBM diet without NSP-enzyme were significantly lower than those in control (P<0.05). Comparing with the SBM diet without NSP-enzyme, the fish fed the SBM diet supplemented NSP-enzyme showed significantly higher SGR (P<0.01), FER, PER, nitrogen and phosphorus retention (P<0.05), and significantly lower nitrogen and phosphorus load (P<0.05). The SGR of fish fed NSP-enzyme pretreated SBM diet was significantly higher than that of the SBM diet without NSP-enzyme (P<0.01), however FER and PER were not significantly different from other treatments (P>0.05).