Preparing method of peracetic acid

The invention provides a continuous synthesis method of peracetic acid. The method includes: a step of measuring acetic acid and hydrogen peroxide with the ratio of the acetic acid to the hydrogen peroxide being 0.4-1.1; a step of mixing the acetic acid and the hydrogen peroxide; a step of feeding the liquid under cooling conditions into an immobilized reactor filled with a solid acid catalyst; and a step of allowing the reaction time of the acetic acid and the hydrogen peroxide in the immobilized reactor to be 1-3 h by adjusting the flow rate so as to obtain the peracetic acid. By the continuous reaction catalyzed by the solid acid and increasing the using amount of the catalyst, the reaction time is shortened, the reaction temperature is lowered, the reaction efficiency is increased, operation is simplified, safety is enhanced, and the peracetic acid with a high concentration is obtained rapidly and conveniently.