The catalytic performance of the carbide slag modified by acetic acid in transesterification was investigated from aspects of molar ratio of methanol to oil, catalyst mass concentration, and reaction temperature and time. Meanwhile, the catalyst was characterized by thermogravimetric analyzer, X-ray diffractometer, N2 adsorption apparatus and Hammett indicator. The length of carbon atoms in peanut oil fatty acids was mainly for 16 to 18. The main component of the carbide slag modified by acetic acid was (CH3COO)2Ca·0.5H2O. And after calcined at 800℃, the catalyst mainly consisted of calcium oxide, with the surface area of 19.07m2/g and the pore volume of 0.0814cm3/g. The catalytic performance of carbide slag modified by acetic acid was better than that of carbide slag under the same conditions. The 96.79% of glycerol yield could be reached under the preferred condition of 15 molar ratio of methanol to oil, 4% catalyst mass concentration, 59℃ reaction temperature, and 2h reaction time. After reused five times, the glycerol yield still remained above 92.90% under the preferred conditions.