Abstract: In order to study the flexural fatigue behavior of glass fiber reinforced polymer(GFRP)-Balsa sandwich beams prepared by a vacuum assisted resin infusion process, four-point fatigue bending tests for 42 specimens under different load levels were carried out. The fatigue failure modes, fatigue life and damage evolution of the sandwich beams were obtained. The damage mechanism of the three types of sandwich beams under bending fatigue load was analyzed. The failure modes of the beams without lattice-web are unified for the core shear failure and debonding, while those of the beams with lattice-web reinforced are varies with the number of lattice-web and the load level, which is buckling or partial crushing of upper facesheet or tensile failure of lower facesheet. The fatigue load-life(S-N) curves of sandwich beams were fitted by exponential empirical model, and the life prediction formulas of three kinds of sandwich beams were obtained. The displacement evolution of the sandwich beams undergoes three stages of "transient fall-stable evolution-damage initiation to failure". Compared with the specimens without lattice-web, the lattice-web reinforced specimens have obvious signs before fatigue failure.