Azelaic acid was synthesized from oleic acid by ozone and hydrogen peroxide as an oxidant jointly. According to the L9 (34) orthogonal form the four factors (including the concentration of hydrogen peroxide, the flow of ozone, different types of tungsten compounds and phase transfer catalyst) on the yield of azelaic acid were investigated under three different conditions. The results show that the yield of azelaic acid Is up to 70.0% under the following condition: oleic acid 20 g, 30% hydrogen peroxide solution 60 mL, phosphotungstic acid hydrate 0.6 g, CTAB 0.5 g, the concentration of Ozne 4 000 mg/m3. The reaction mechanism of azelaic acid synthesis was also studied, and found that •OH is an important reactant.