Abstract: Purple passion fruit as the study object in this paper,effects of different kinds of acid extraction solvent on the determination results of vitamin C in the purple passionfruit,effects of material to solvent ratio,ultrasonic time and ultrasonic power on the extraction of vitamin C were studied by single factor and response surface methodology. The results showed that 2% oxalic acid was the best extraction solvent for vitamin C from purple passion fruit,and the optimal extraction technology was as follows:material to solvent ratio 4:1 mL/g,ultrasonic temperature 43℃,ultrasonic time 18 min,ultrasonic power 310 W,the vitamin C content of purple passion fruit was 0.5316 mg/g,the results are close to the theory of the prediction.