Abstract: The fatigue tests of concrete under biaxial compression with constant confined stress were performed using the static-dynamic triaxial test system. The failure modes of concrete specimens were acquired. The uniaxial test results of fatigue were compared with those obtained by other researchers for validity. The laws of compressive fatigue strength and deformation are analysed based on the results of experiment. The relationship of S-N under certain lateral stress is established and from which the unified fatigue equation accounting for different confined stresses is derived. The results of investigation in this paper offer the basis for design and analysis of concrete structures subjected to triaxial cyclic loading.