Soybean oil and rapeseed oil were taken as the research objects, and the sensory quality and characteristic indexes changes during the frying process for 15 hours at 170 ℃ were discussed. Meanwhile, the relationship between fatty acid composition, polar component, viscosity value and high value of oil bubble was studied. The results showed that the sensory experience of soybean oil in the frying process was better than that of rapeseed oil. The changes of acid value of the two kinds of oils were within the hygienic standard (acid value≤5 mgKOH/g), and there was a significant positive correlation between the bubble high value, viscosity, polar components and the frying time (P<0.01). In addition, viscosity and polar components were also positively correlated with bubble height respectively (P<0.01). The relative content of total saturated fatty acids in vegetable oil will increase gradually, which has a significant positive correlation with the bubble high value (P<0.01); the relative content of total unsaturated fatty acids will decrease gradually, which has a significant negative correlation with the bubble high value (P<0.01), and the content of total trans fatty acids will decrease gradually, which has a significant negative correlation with the bubble high value (P<0.01).