Barrel polishing (also called CBP or roll grinding and polishing) is generally used in polishing treatment of cell type Niobium cavity wall and able to remove irregularities like scratches and especially any roughness at electron beam weld seams.The mixtures of water and ceramic particles or plastic particles are put in Niobium cavity.By means of horizontal rotary of cavity,the polishing effect can be achieved by centrifugal force which leads to relative movement between abradant and cavity wall.Before chemical treat- Barrel polishing (also called CBP or roll grinding and polishing) is generally used in polishing treatment of cell type Niobium cavity wall and able to remove irregularities like scratches and especially any roughness at electron beam weld seams. Mixtures of water and ceramic particles or plastic particles are put in Niobium cavity.By means of horizontal rotary of cavity, the polishing effect can be achieved by centrifugal force which leads to relative movement between abradant and cavity wall.Before chemical treat-