Fatigue tests of concrete under constant amplitude biaxial tension compression and triaxial tension compression compression cyclic loading were carried out using a large multiaxial fatigue testing machine. Fatigue failure mode, fatigue strength and residual strain of concrete under different lateral stress ratios and different stress levels were analyzed. The stress level fatigue life(S N) curve of fatigue life and corresponding expressions were obtained. The results show that the multiaxial fatigue failure mode of concrete is independent of the lateral stress ratio under constant amplitude cyclic loading; the residual strain develops in three stages, and it is greatly affected by the lateral stress ratio but almost independent of the stress level. Furthermore, the relative residual strain is defined as the damage variable, and the damage evolution equation is established, which provides reference for multiaxial constant amplitude fatigue experimental research and damage evaluation of concrete.