An 8-week feeding trial was conducted in a recirculated system to study the effect of dietary DHA to EPA ratios(0.64,0.97,1.18,1.59 and 1.91),with 0.74% n-3 HUFA and 8.3% lipid in dry feed,on growth performance,body composition and blood biological parameters in juvenile starry flounder,Platichthys stellatus.The results showed that:(1)fish weight gain rate(WGR),feed efficiency(FE),as well as protein efficiency ratio(PER)increased and then decreased with higher DHA/EPA values(P<0.05).Quadratic regression(y=-1.589 5x²+2.858 3x+45.184;R² =0.910 8,x=dietary DHA/EPA ratios,y=PRE)showed PRE decreases significantly beyond the DHA/EPA ratio of 0.90.Spleensomatic index(SSI)was enhanced by dietary DHA/EPA ratios and showed highest values of 0.12% in DHA/EPA ratio of 1.59,whereas hepatosomatic index(HSI)was decreased and then increased by dietary DHA/EPA ratios(P<0.05),with the lowest value being in DHA/EPA ratio of 1.18(2.85%).(2)Liver lipid was obviously decreased(from 13.44% to 8.60%)by dietary DHA/EPA ratios lower than 1.18,and then increased slightly.Quadratic analysis(y=5.199 6x²-15.652x+20.866;R²=0.634 8,x=dietary DHA/EPA ratios,y=liver lipid content)suggests the optimum DHA/EPA ratio is 1.51 based on liver lipid deposition.Liver and muscle EPA contents were reduced linearly,however,DHA contents as well as DHA/EPA ratios were elevated linearly by dietary DHA/EPA ratios.Exclusively,total content of n-3 HUFA in both tissues were unaffected by dietary treatments.(3)Among all serum physiological parameters,both total protein and globulin showed their highest values at the DHA/EPA ratio of 1.59,while fish fed diets with DHA/EPA ratios of 0.64,0.97 and 1.59 presented higher albumin content.Lysozyme(LSZ)reached the top in fish fed diet with dietary DHA/EPA ratio of 1.18.Alanine aminotransferase(ALT)remained unchanged when the dietary DHA/EPA ratios were lower than 1.91,while dietary DHA/EPA ratios higher than 1.18 increased the aspertate aminotransferase(AST)activities by about 65%(P<0.05).In conclusion,under the present experimental conditions,based on fish weight gain rate(WGR),quadratic regression analysis(y=-31.066x²+77.26x+76.541;R²=0.957 4,x=dietary DHA/EPA ratios,y=weight gain rate)shows that the optimum DHA/EPA ratio for juvenile starry flounder[initial body weight,(31.70±0.12)g]is 1.24.