Abstract: In order to reveal the influence of carnosic acid on the quality characteristics of thermal processed rapeseed oil, the changes of color, acid value, peroxide value, tocopherol, viscosity, fatty acid composition and total polar compound were investigated during thermal processing (180 ℃, 0, 8, 16, 24, 32 h) by adding different concentrations of carnosic acid (0, 200, 400, 700 mg/kg) and 200 mg/kg tert-butylhydroquinone as antioxidants. The results indicated that the addition of 700 mg/kg carnosic acid showed a better performance in the thermal processed rapeseed oil: The color deterioration was delayed and the increase of viscosity was inhibited; the increased value of acid value was the smallest which was from 0.280±0.030 mg/g to 0.757±0.020 mg/g, as well as the minimum peroxide value (0.138 g/100 g) was obtained at 32 h; the loss rate of α-tocopherol and γ-tocopherol were 95.51%±0.96% and 83.37%±0.39%, respectively; the content of polar components was 26.62%±0.03%, prolonging the thermal processing life of rapeseed oil by delaying the increase of total polar compound. It was found that the use of carnosic acid could better control the risk factors in rapeseed oil during thermal processing and reduce the waste of oils.