Abstract: There are many reports about increasing yield of Application Phosphorus and lack of Phosphorus on red soil, but less reports about the residual effect of application phosphorus on red soil of a long-term experiment. The author spends about 20 years studying the residual effect of application phosphorus. The results showed as follow. There is the residual effect after stopping application different amount of phosphorus-20 years. Some years the residual effect is also higher than the quarter-phosphorus fertilizer efficiency. The amount of application phosphorus and the residual effect of phosphorus is positively correlated. Phosphate fertilizer units and the residual effect of phosphorus show decreasing trends. Different treatment of residual effect of phosphate fertilizer with time extended decline. Corn planted on the soil which lack of phosphorus will not affect its nitrogen absorption. Farmers applying manure on red soil drylands can promote the decomposition of insoluble phosphate, and increase available phosphorus content in soil. If after using P2O5120kg/hm2 on red soil drylands for six consecutive years, and then stopping 4 to 5 years, the output will increase because of the residual effect of application phosphorus. This article provides a scientific basis for scientifically applying phosphate on red soil drylands.