Abstract: Under different simulated rainfalls the root properties and soil available nutrient for summer corn with ridge and furrow planting of rainfall harvesting(RFPRH) were studied to investigate yield increase mechanism and fitting rainfall of RFPRH system. The results showed that contents of available N, P and K in topsoil(0～40 cm) treated with RFPRH increased significantly(p＜0.05). Under 230 mm and 340 mm, the root length, root superficial, root volume and root dry matter weight significantly increased, while under 440 mm the corresponding value decreased respectively(p＜0.05). And the increase of seed yield decreased with rainfall increase in 230～440 mm(p＜0.05). And the effect of yield increase wasn't significant at 440 mm. Therefore, the application of RFPRH can not only improve the relationship of soil water and nutrient but also the root growth of plant at fitting rainfall. Under this planting pattern, the fitting max rainfall for planting maize could be about 440 mm during the whole growth stages.