To analyze the triaxial mechanical properties of coral seawater sea sand concrete, the effects of aggregate and lateral confining pressure on the failure mode, stress-strain curve, yield stress, yield strain, and damage evolution of specimens were investigated via conventional triaxial tests. The results show that the coral coarse aggregate specimen is more susceptible to the influence of confining pressure value. The cracks form transformation and plastic flow appear on the surface of the specimen at a confining pressure value of 9 MPa. The stress-strain curve appears a stress platform section' at a confining pressure value of 12 MPa, while the gravel coarse aggregate specimen appears the above changes at confining pressure values of 15 MPa and 24 MPa, respectively. After a confining pressure value reaches 15 MPa, the stress-strain curve of the coral coarse aggregate specimen shows a bilinear shape with a second linear branch. The dissipation energy of the specimens gradually increases and the damage development gradually delays with the increase of confining pressure, yield stress and yield strain. In addition, the yield stress calculation formula of coral seawater sea sand concrete was aslo proposed, thus providing a reference for the relevant theoretical analysis and engineering application.