Abstract: The 3-point bending test was performed on Material Testing System(MTS) to investigate the quasi-static and fatigue behavior of ultra-thick 3-D orthogonal woven composites(glass/unsaturated resin),which aimed to predict the fatigue property of this material.The results revealed that the fatigue degradation of the material includes three stages: micro-crack appearing at initial stage,a long process of crack propagation and fatigue failure of the material after suffering the extraordinary degradation of stiffness.In addition,the fiber volume fractions of composites have great impact on the quasi-static mechanical property and play a decisive role in the fatigue behavior.Comparisons made between experimental data and a theoretical fatigue model show good agreement,which can be used to predict the fatigue residual modulus of composites.