Abstract: The stress-strain characteristics and damage evolution of polypropylene fiber coral seawater concrete (PPF/CAC) under uniaxial cyclic compression were studied. A total of 20 samples with different fiber volume fractions were tested. The failure form of PPF/CAC was observed in the test, and the stress-strain curve, peak stress-strain, plastic strain and other important indexes were obtained. The results show that the strength of specimens under cyclic loading is reduces by 1.21%-3.67% compared with that under monochrome loading, and the degradation can be slowed down with the increase of fiber content. The peak stress and peak strain increases are the largest when the polypropylene fiber volume fraction is 0.15vol%, which are 10.45% and 6.45%, respectively. In addition, the increase of PPF volume fraction can significantly reduce the accumulation of plastic strain and increase the elastic stiffness ratio. According to the test results, four characteristic points of hysteresis curve are defined: Unloading point, common point, residual point and end point. And the relationship between residual strain, common point strain and end point strain and unloading strain is established. Finally, the stress-strain constitutive equation and damage constitutive model of PPF/CAC under cyclic load are proposed, and the simplified stress-strain constitutive equation based on the damage evolution law can effectively predict the stress-strain behavior of PPF/CAC under cyclic load.