To study the VOCs removal in cooking oil fume, the degradation of butyraldehyde as the target pollutant by Mn2+ catalytic ozonation was studied, the reaction conditions that affect the removal efficiency of butyraldehyde including the presence or absence of Mn2+, pH, catalyst concentration, the initial concentration of butyraldehyde, \[O₃\]/\[butyraldehyde\] concentration ratio, temperature were investigated . The results showed that: the addition of Mn2+ can significantly improve the removal efficiency of butyraldehyde, and the removal efficiency improved with the decrease of the concentration of butyraldehyde and the increase of \[O₃\]/\[butyraldehyde\] concentration ratio. The degradation rate firstly increased then decreased with the increase of the concentration of Mn2+ and temperature, reaching the optimization when at 1 mmol/L and 30 ℃, respectively. The optimal pH existed, which is 5.When catalyst concentration was 1 mmol/L, pH =5,the initial concentration of the butyraldehyde 200 mL/m³,\[O₃\]/\[butyraldehyde\]= 0.2, under the room temperature, the removal rate of butyraldehyde is 94.67%, mineralization is 91.8%.