The effect of four frying processes (vegetable salad, stir frying, pan frying, and deep frying) on fatty acid composition of ten vegetable oils (peanut oil, soybean oil, rapeseed oil, corn oil, sunflower seed oil, rice bran oil, olive oil, sesame oil, linseed oil, and peony seed oil) was investigated using GC-MS. The result showed that trans-fatty acid (TFA) was produced during all processes. Rapeseed oil had the highest TFA content in vegetable salad oil with 2.88% of total fatty acid. The TFA content of sunflower seed oil was 0.00% in vegetable salad oil, however, after stir frying and pan frying, it increased to 1.53% and 1.29%, respectively. Peanut oil had the lowest TFA content after deep frying for 12h with 0.74mg/g. It was concluded that a healthy cooking process could be acquired by a scientific collocation.