An experimental system has been set up for producing extreme ultraviolet light with high conversion efficiency by employing high power YAG laser irradiated tin slab. The dependence of extreme ultraviolet light intensity and conversion efficiency on the pump energy were studied， and the saturation effect of conversion efficiency was observed. The highest conversion efficiency of 1.6% in producing 13.5nm extreme ultraviolet light with 0.27nm bandwidth was achieved at pump energy of 250mJ, which corresponds to an intensity of 1.8×1011W/cm2.