A field experiment was conducted to determine the effects of rainwater-harvested furrow/ridge systems on soil water use efficiency (WUE) and grain yield of spring com under differently simulated rainfall supplies. Our results showed that when rainfall supply ranged between 230 and 440mm, rainwater-harvested furrow/ridge system could increase the surface temperature at a depth of 10cm by 0.7-1℃ and water storage capacity in the 0-120cm soil layer by 5%-12%,as well as speeded up the emergence of seedlings compared with the control. In addition, this rainwater-harvested furrow/ridge system also enhanced grain yield and WUE of spring com by 82.8% and 77.4% under rainfall of 230mm, by 43.4% and 43.1% under rainfall of 340mm and by 11.2% and 9.5% under rainfall of 440mm. The upper ceiling of rainfall for spring com suitable for adopting this furrow/ridge system was considered to be about 440mm over the whole growth period of com.