With salicylic acid and acetic anhydride as raw material,and potassium aluminum sulfate to weak acid as a catalyst,the acetylsalicylic acid can be synthesized easily.The experimental results show that：the reaction temperature,reaction time,catalyst amount,the ratio of salicylic acid,acetic anhydride and other factors are influential to that.The best reaction conditions are：0.6g catalyst,n（acid）：n（acetic anhydride）= 1.0：2.0,constant temperature at 70 degrees,30min reaction time,with optimal reaction conditions,the acetyl acid production rate was 77.8%.The results also show that the production rate is higher with the aluminum potassium sulfate as a catalyst than that with concentrated sulfuric acid as catalyst,and product color is white,and with high purity.