Abstract: Nowadays there are two main methods used for the recovery of altered VIN in China. One is scrubbing with chemicals (chemical reaction between metal and acid), the other is magnetic recover by the related instrument. In this paper, the results of these two methods are compared to show that the advantage of the latter one is simple and convenient, but the effect of its appearance is not superior to the chemical reagent cleaning method. In addition, the price of the instrument is more expensive and its application in the inspection and appraisal practice has certain limitations.