Biofloc systems represent a promising approach for achieving greater sustainability and productivity in aquaculture. This trial aimed to investigate the physio-histological impacts of different concentrations of biofloc on antioxidant capacities and the histology of both hepatopancreas and gills structure and abnormalities of the white leg shrimp (Litopenaeus vannamei). The study used three ratios of C:N (1:10, 1:15, 1:20) with three different levels of density (10, 20, 20 individuals/100L) for each ratio with triplicate for 56 days. The results of antioxidants activities showed that antioxidants (SOD, CAT, GPXs, MDH, LYZ) were significantly increased in biofloc treatments and reached its best activity in 1:15 treatment with a stocking density of 20 individuals/100L. The histological records indicated that 1:15 ratio enhanced the structure for both hepatopancreas and gills tissues. Tissues in the control and 1:10 ratio treatment seemed to be normal. In the 1:15 treatment, the hepatopancreas showed all important cells as blaze-Zellen cells (B) and embryonal Zellen cells (E) and normal arrangement of cells and normal interlamellar space for gills. With the increase of C:N ratio and stocking density, hepatopancreas showed a severe cell deformation, vacuoles, while the gills showed epithelial edema and abnormalities, particularly in 1:30 treatment, with 30 individuals/100L.