Acid treated activated carbon was used as a catalyst for heterogeneous catalytic ozonation of cinnamaldehyde to natural benzaldehyde. The effects of the solvents type, dosage of ethanol and activated carbon, ozone flow rate, and ozonation reaction temperature on the reaction of catalytic ozonation of cinnamaldehyde to benzaldehyde on activated carbon were investigated. The results show that the utilization of ozone can be improved by using activated carbon as catalyst, and the utilization of ozone was increased from 53.5% of the ozone alone to 67.4%. The optimal reaction conditions were as follows: ethanol was used as solvent, the mass ratio of ethanol to cinnamaldehyde was 3, oxygen flow rate was 800 mL/min (ozone flow rate was 0.71 g/h ), the mass ratio of activated carbon to cinnamaldehyde was 0.01, reacted at 0 ℃ for 2 h, the yield of benzaldehyde was 44.0%.