The utility model discloses a burnishing device of variable cross section part, including tungsten carbide slug, steel bloom and magnet, the below of steel bloom is equipped with a recess, and magnet is inlayed in the recess, the upper surface of arranging the steel bloom in of tungsten carbide slug symmetry, the upper surface of steel bloom is equipped with four tungsten carbide slugs at least, the lower part branch of magnet is equipped with the through -hole. The utility model discloses a divide the pattern fixture fixed sample, polish it, make things convenient for the sample to grip, grind and polish. This utility model method is simple, with low costs.