To study the axial compression performance of coral aggregate seawater sea-sand concrete (CSSC) columns confined with carbon fiber reinforced polymer-polyvinyl chloride composite tube (CFRP-PVC), six specimens were subjected to axial compression load tests and finite element parameter analysis. The effects of the number of CFRP layers on inner and outer surfaces of PVC tube and void defects on the axial compression performance of composite column were studied. The results show that CFRP-PVC tube can effectively confine CSSC, placing it in a triaxial compression state. When CFRP is pasted on both the inner and outer wall with tube, it can effectively alleviate the characteristic of sudden failure. With one layer of CFRP pasted on the inner wall of PVC tube, better ductility and bearing capacity can be achieved under same conditions. With two layers of CFRP pasted on the outer wall of PVC tube, the coefficient of constraint stress increase is as high as 121.5%, and the void defects only have a significant impact on ductility. A finite element model of CSSC column confined with CFRP-PVC tube is established based on ABAQUS software, accurately restores the failure process and CFRP damage morphology of composite columns under axial load. Parameter analysis shows that when the confinement coefficient of composite column is less than 0.3 or the aspect ratio is greater than 14.54, the load-displacement curve will lose strengthening section. Increasing the number of outer CFRP layers will slightly increase the stiffness of strengthening section. A bearing capacity calculation method suitable for CSSC column confined with CFRP-PVC tube is proposed, with an error of 1.2%.