The quality change of sunflower oil, which was rich in oleic acid and linoleic acid, during frying process was explored. The results showed that: sunflower oil fried for 24 h at190±5 ℃, the acid value increased from 0.26 mg/g to 0.89 mg/g, peroxide value increased from 4.40 mmol/kg to 8.20 mmol/kg, carbonyl value rose from 8.39 meq/kg to 74.47 meq/kg, the content of malondialdehyde rose from 0.25 mg/100 g to 2.07 mg/100 g, the content of total trans-acids increased from0.45% to 1.40%, the content of vitamin E reduced from 39.52 mg/100 g to 14.23 mg/100 g and polar component rose from 3.80% to 35.30%. Among the results, carbonyl value reached to 44.44 meq/kg when fried for 12 h and the content of polar component reached to 26.70% when fried for 18 h, which was close to the index in GB 7102.1—2003 Hygienic standard for edible vegetable oils during frying. So, sunflower oil is not suitable frying food at high temperatures for a long time. And the frying time should be less than 12 h.