Abstract: A new antioxidant biodiesel isopropyl gallate was prepared by using gallic acid and isopropanol as raw materials, pyridine bisulfate ionic liquid as catalyst. Through the single factor analysis, the optimal reaction conditions of catalytic esterification reaction were obtained as reaction time 4 h at 85℃, the ratio of alcohol to acid 35:1, catalyst dosage 12%, the yield of isopropyl gallate under these conditions was 89.1%. Based on the catalytic esterification reaction dynamics analysis, the reaction apparent activation energy and the frequency were obtained as 60.942 kJ/mol and 7 060 313.404, respectively. The addition of 0.05% isopropyl gallate in gallate in gutter oil biodiesel significantly improved the oxidation stability, and the induction period increased from 0.61 h to 6.34 h, which completely reached the national standard for biodiesel(induction period 6 h). The experimental results showed that isopropyl gallate had good performance as new biodiesel antioxidant.