Abstract: Chinese sturgeon (Acipenser sinensis) is a large anadromous migratory fish. In order to understand the immune characteristics of freshwater cultured Chinese sturgeon in seawater, a 5-month mariculture trial was conducted with 4-year-old Chinese sturgeons, and the adaptive changes of blood physiology, biochemistry and immune tissue were explored. The results showed that the white blood cell counts were significantly increased (P<0.05), and there was no significant difference on red blood cell count, but the hemoglobin and hematocrit increased significantly in the seawater from (46.50±10.59) g/L, (13.70±3.23)%, (9.19±1.10)×10⁹/L to (74.50±11.05) g/L, (21.80±3.33)% and (10.88±3.73)×10⁹/L, respectively. In the differential count of white blood cells, lymphocytes accounted for the largest proportion, followed by neutrophils, and there was no significant difference in the percentages of various types of white blood cells. Blood biochemical indexes such as SOD, MDA, LZM, IgM, AKP and ACP have no significant changes in freshwater and seawater. Observation of immune tissue structure showed that there was no obvious change in the thymus in seawater, but the cells were aggregated, the shape distribution was more orderly and the center of melanin macrophages increased in the head kidney tissue; Lymphocytes and red blood cells are more densely distributed in the spleen tissue. The results showed that marine aquaculture can enhance the immunity and hematopoietic function of Chinese sturgeon to a certain extent, and maintain a good physiological state.