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The experiment was to investigate the effect of Chlorella powder and Haematococcus pluvialis on growth, antioxidant capacity and midkidney tissue structure of juvenile Epinephelus lanceolatus♂×Epinephelus fuscoguttatus♀. A total of 540 fish were randomly divided into three groups, with three replicates in each group and 60 fish in each replicate. Fish in DZ group were fed with a basal diet, fish in experimental groups were fed with basal diet supplemented with 10% Chlorella powder (Chl group) and 10% Haematococcus pluvialis powder (Hap group), respectively. The experiment lasted for 60 d. The results showed that compared with DZ group, on 15 d there were no significant differences in weight gain rate, specific growth rate, liver body ratio, spleen body ratio and fatness between Chl group and Hap group (P>0.05). On 60 d, HSI of Hap group was 4.95%, which was significantly higher than that of DZ group (P<0.05). On 15 and 60 d, the activity of AKP in middle kidney of Hap group was significantly higher than that of DZ group (P<0.05). On 60 d, CAT activity in Chl group was significantly lower than that in DZ group (P<0.05). Microscopic observation showed that the epithelial cells of renal tubules in DZ group showed mild hyaline degeneration, the nuclei of epithelial cells of some proximal and distal convoluted tubules disappeared. The cell structure of Chl group and Hap group was intact without obvious tissue lesion. The experiment indicates that the addition of Chlorella vulgaris and Haematococcus pluvialis in juvenile Epinephelus lanceolatus♂×Epinephelus fuscoguttatus♀ diet can improve the antioxidant function and repair the tissue damage, but has no significant effect on the growth performance of fish. [ABSTRACT FROM AUTHOR]