Abstract: In order to know the extraction process by ethanol companied ultrasonic method of chlorogenic acid (CHA)in fruit of Prunus mume, the effects of ethanol concentration, solid-liquid ratio, pH value, ultrasonic time, ultrasonic temperature and extracting times on extraction of CHA were studied, also the oxygen radical absorbance capacity (ORAC)of CHA was measured in this paper. The results showed that the optimal extraction processing parameters of CHA in Prunus mume fruit were 60% ethanol, 1:7 (g:mL)solid-liquid ratio, pH4, 30 min ultrasonic time, 50℃ ultrasonic temperature and 3 extraction times. Under this condition, the total yield of CHA could reach 19.8 mg/10 g fresh weight. The ORAC value of CHA was 258869 mmol/g, while ORAC value of rutin was 155981 mmol/g. There was significant difference between the oxygen radical absorbance capacities of CHA and rutin. From these results, we could draw that the content of CHA in Prunus mume fruit is high and CHA has strong antioxidant activity to many oxidants. CHA was an important antioxidant constituent in Prunus mume fruit.