Abstract: This study aimed to explore the effects of adding Schizochytrium meal to the feed on the growth performance, digestive physiology, immune antioxidant capacity, and intestinal flora diversity of sea cucumbers (Apostichopus japonicus), providing a theoretical basis for the application of Schizochytrium meal. The initial weight of the sea cucumbers was (1.09±0.02) g. Five experimental feeds were formulated with Schizochytrium meal contents of 0 (AP0, control group), 0.80% (AP2), 1.60% (AP4), 2.40% (AP6), and 3.20% (AP8). A 56-day growth experiment was conducted to evaluate the effects. The results showed that the addition of Schizochytrium meal significantly increased the weight gain rate and specific growth rate of sea cucumbers (P<0.05), with trend was first increasing and then decreasing with the increase of the addition amount. The optimal growth performance was observed at a 2.40% inclusion level. Compared with the control group, the crude fat content in the body wall of sea cucumbers in the Schizochytrium meal addition groups was significantly reduced (P<0.05), while there was no significant difference in other body wall nutrients among the groups. In addition, the activities of intestinal trypsin, lipase, acid phosphatase, alkaline phosphatase, superoxide dismutase and lysozyme first increased and then decreased, reaching the maximum value in the AP6 group. Similarly, catalase activity first increased and then decreased, reaching the maximum value in the AP4 group. The height of intestinal folds in the AP4 and AP6 groups was significantly greater than that in the control group, and the thickness of the muscular layer reached the maximum value in the AP6 group. Moreover, Schizochytrium meal increased the Ace index, Chao index and Sobs index of intestinal flora, with Proteobacteria, Verrucomicrobia and Planctomycetes jointly became the dominant bacteria phyla. In conclusion, the addition of 2.4% Schizochytrium meal in the feed can enrich the diversity of intestinal flora, promote the intestinal digestive function and immune antioxidant capacity, and improve the growth performance of sea cucumbers.