The invention provides a method for extracting tanshinone IIA, wherein the method comprises the steps: (1) sending a salvia miltiorrhiza medicinal material after pretreatment into a supercritical CO2 extraction device, taking ethanol with the concentration of 90-95 wt% as an entrainer, and carrying out supercritical extraction, to obtain an extract liquid; and (2) carrying out rotary evaporation concentration on the extract liquid obtained in the step (1), to obtain the tanshinone IIA. According to the method, with the ethanol with the concentration of 90-95 wt%, the tanshinone IIA in the salvia miltiorrhiza medicinal material is extracted out to a largest extent at a time through supercritical CO2 extraction, and the extraction rate is relatively high. The method greatly reduces the extraction and separation steps, is simple to operate, can save a lot of organic solvents, and effectively solves the problems of low tanshinone IIA content, low extraction rate, large use amount of ethanol, low production operation safety coefficient, high production cost and the like caused due to more purification refining steps, complex process and incomplete impurity removal.