Abstract: The present trial was conducted to investigate the dietary vitamin B₆ requirement of sea cucumber Apostichopus japonicas Selenka juveniles. The experimental diets were formulated with graded levels of vitamin B₆ (1.23, 5.29, 9.35, 17.47, 33.71, 66.17 mg/kg), and named D1, D2, D3, D4, D5 and D6 groups. Each diet was randomly assigned with triplicate sea cucumber juveniles with initial body weight (12.23±0.11) g for 12 weeks. The results showed that weight gain rate and specific growth rate presented increasing first and then decreasing afterwards, and got maximum in D5 group. Crude protein of body wall was increased first with dietary vitamin B₆ and then decreased, and crude protein of D6 group was significantly lower than other groups; Crude lipid of D1 group was significantly lower than other groups. All of activities of glucose 6-phosphatede hydrogenase, isocitrate dehydrogenase, acetyl coA carboxylase, and nitric oxide synthesis were increased first and then decreased afterwards, activity of D6 group was significantly lower than other groups. With the increasing of dietary vitamin B₆, both protease and amylase were increased, and cellulase was decreased with dietary vitamin B₆, while the height of villus, MC and the thickness of muscularis were increased significantly. With the weight gain rate as the evaluation indictor, regression analysis showed that the optimum dietary vitamin B₆ requirement for sea cucumber juveniles was 45 mg/kg.