Abstract: Using carbon-based solid acid as catalyst synthesized from starch and P-Toiuene Suitonic acid, oleic acid as raw materials to simulate the high acid value of raw materials for biodiesel was explored to reduce the acid value, and the amount of catalyst, the ratio of methanol to oleic acid, reaction temperature, reaction time and reusability were investigated. The optimum conditions were determined with the single factor and orthogonal tests. The experimental results showed that the conversion rate of oleic acid was 78.82% by following conditions: the ratio of methanol to oleic acid was 1︰4 (W/W), carbon-based solid acid was 6.5% (W/W) as catalyst, esterification reaction temperature was 85℃ and reaction time 6 h. The conversion rate still maintained above 70% after repeatedly using 6 times. The carbon-based solid acid catalyst has high catalytic activity, easy separation, good stability.