The invention relates to a one-valve three-control jetting method for a urea reducer. The method is characterized in that the pipeline of a urea reducer box is connected with a filter in series, wherein an electromagnetic flow control valve connected with the filter is provided with three outlet ends which are connected with precise mechanical switching valves in parallel respectively and connected with a pressure maintaining valve, a urea reducer nozzle and an exhaust pipe in turn; one, two or three of the three parallel precise mechanical switching valves acquire signal analog quantity of a temperature sensor or NOX sensor independently or in groups and feed the signal analog quantity into a control unit; one, two or three outlets of the electromagnetic flow control valve are independently opened by the control unit according to set control logic; and a control platform with seven measuring levels is formed after secondary calibration of the precise mechanical switching valves. The method can meet national selective catalytic reduction (SCR) standard requirements over four; and in the method, the NH3 escape volume is not generated, and a diesel oxidation catalyst (DOC) device for performing oxidation treatment on NH3 can be saved, the vehicle configuration is simplified and the cost is reduced.