A self-excited hydrodynamic cavitation jet reactor combined with ozone oxidation has been used to treat salicylic acid wastewater, and the degradations of salicylic acid by hydrodynamic cavitation, ozone oxidation and their combination were compared. The results show that the maximum salicylic acid removal rate is only 3.89% when the salicylic acid wastewater is treated by hydrodynamic cavitation for 60 min under different working conditions. Under the same conditions, the maximum removal rates of salicylic acid by ozonation alone and the combined treatment of the two methods were 61.47% and 70.63%, respectively. At an ozone flow rate of 0.6-1.0 L/min, the synergistic coefficient of the combined treatment was greater than 1, indicating that the combined system had a synergistic effect. When the ozone flow rate was 0.8 L/min, the synergistic coefficient of the combined system reached a maximum (1.306), and the removal rates of salicylic acid and total organic carbon (TOC) were 58.51% and 29.94%, respectively, after combined treatment for 60 min. When the ozone flow rate was greater than 0.8 L/min, the synergy coefficient decreased, indicating that too much ozone might weaken cavitation and ozone mass transfer.