Abstract: Artificial UV irradiation aging test under warm-wet environment was conducted for glass fiber reinforced unsaturated polyester resin composite. The effect of UV aging on mass loss rate, barcol hardness, tensile and bending mechanical properties and their failure patterns of composite was studied. The structure and micro morphology were analyzed. Results show that the mass loss rate of composite increased continuely with the increase of UV aging time.The barcol hardness of the irradiated surface was lower than that of non-irradiation surface, and the retained rate of barcol hardness increased first and then dedecreased with the increase of UV aging time. The tensile and bending strength of composite were improved first and then decreased slowly. Cavity density and tenacity white stripe in composite after aging increased, and it presented obvious lamellar wave pattern. Repture of chemical bonds took place in composite and UV irradiation made the structure changed.