Abstract: To meet the rural grassroots’ needs of low-cost, personalized and quick testing soil for formulated fertilization, solve the problem that the available nitrogen can not be determined by using the existing universal soil extractants in humble conditions or when the mobile services, study a combined soil extractant that can be used for calcareous or neutral soil to leach nitrogen, phosphorus and potassium at the same time. On the base of soil chemistry, using correlations analysis method, this study presents the combined leaching agent is made with sodium bicarbonate and sodium sulfate so that it can be applied to the ready fertilizer technology system easily. Study results show that using it can shorten more than two-thirds of leaching time, and the correlations between speed measurement values and conventional test value are extremely significant (a=0.01). And the testing cost for nitrogen, phosphorus and potassium of soil is reduced more than tenfold by using it on XUNJIE soil rapid detection. It is suitable for the application of soil testing and fertilization in the grass or mobile service vehicles as it can meet the rural grassroots’ needs of low-cost, personalized and quick testing soil for formulated fertilization.