Purifying process for solution of wood vinegar

The invention relates to a method of the purification technology of pyracetic acid. The method is characterized in that the method comprises the following steps: firstly, the stock solution in a stock solution bath is fed into a two stage pre-filtration system and a two stage secondary precision filtration system which are connected in series to be filtered; secondly, the filtered solution obtained in the first step is fed into multistage membrane separating systems which are connected in series at intervals in sequence and are composed of at least three stage membrane separating devices and three water washing boxes to be separated; wherein, the concentrated water separated through the primary stage membrane separating device is respectively fed into the stock solution bath and a concentrated water tank; the concentrated water separated through the secondary stage membrane separating device is fed into the concentrated water tank through a pipeline; the concentrated water separated through the tertiary stage membrane separating device is respectively fed into the first water washing box and the second water washing box through a pipeline; finally the concentrated pyracetic acid with 50 percent of content is obtained in the concentrated water tank, and the separated fresh water is discharged after being metered through the third water washing box.