Abstract: In order to better directly apply the undisturbed seawater sea-sand coral concrete to marine engineering, this paper performed a monotonous study on 12 carbon fiber reinforced plastics (CFRP)-steel composite tube filled circular seawater sea-sand coral concrete columns and 2 pure steel tube confined seawater sea-sand coral concrete columns. In the axial compression test, the main research parameters are the diameter-thickness ratio of the steel tube and the number of CFRP layers. The test has obtained the axial stress-strain relationship curve of the specimen. The results show that the specimen is in the form of shear failure with obvious shear slip line at the end of the column under axial pressure. The constraint effect of CFRP has no obvious effect on the initial section stiffness of the specimen, but has a significant effect on the stiffness of the specimen in the linear strengthening stage. With the increase of the number of CFRP layers, the ultimate stress and strain of the specimens are significantly increased. With the decrease of the diameter-thickness ratio of the steel tube, the mechanical properties of the specimens increase correspondingly. Combined with the test data, the existing FRP steel composite pipe confined concrete strength calculation model was evaluated.