Abstract: Using the composite method of the following three steps to get carnosic acid from rosemary leaves, the purity of carnosic acid was 21.06% by ultrasound-assisted ethanol extraction. The purity of carnosic acid was 79.62% by ultrasonic-assisted n-hexane extraction and pH adjustment. The optimization conditions of ultrasonic-assisted n-hexane extraction were liquid/solid ratio 20:1(mL:g), ultrasonic frequency 28 kHz, ultrasonic time 40 min, ultrasonic power 140 W. Under these conditions, the yield of carnosic acid was 2.0%. The optimization conditions of silica gel column chromatography were particle sizes of silica gel 48-75 μm, the volume ratio of eluent ethyl acetate and petroleum ether 4:7, the flow rate 6 mL/min and 0.3 g solid loaded. The recovery rate of carnosic acid was 54.12%. The purity of carnosic acid was 95.18% by this method.