The invention discloses a selective extraction method of mulberry alkaloid. The method comprises the following steps: (1) cleaning mulberries, draining, and pulverizing; (2) preparing an extraction agent; (3) adding the extraction agent into mulberry powder, magnetically stirring at the temperature of 50 to 80 DEG C, filtering, and adding an ethanol aqueous solution; (4) two-phase digestion: adding ammonium sulfate, severely stirring, standing, layering, and collecting an alkaloid layer with relatively dark color; (5) performing dialysis to remove impurities, adjusting the pH of a sample to be slightly alkaline, placing the sample into a rotary evaporator, decompressing, distilling, evaporating and recycling the extraction liquid, and drying a product in the evaporator under a vacuum condition to obtain the mulberry alkaloid. The selective extraction method has the incomparable advantages of the traditional extraction technology that the extraction selectivity of the alkaloid is high, a purification effect can be realized while in extraction, the extraction time is short, the extraction yield of active ingredients is high, and no special separation step is needed.