The invention relates to a clamping device and polishing method for plate-type products. The clamping device is used for assisting in polishing the side faces of the plate-type products and comprisesa retainer, a clamping assembly and a locking mechanism; the locking mechanism can lock the clamping assembly on the retainer or release the locking state to enable the clamping assembly to be separated from the retainer; the clamping assembly comprises a supporting member, a pressing member and multiple product locating members capable of being stacked, the pressing member can be tightly connected with the supporting member and makes the stacked product locating members pressed mutually, thus every two adjacent product locating members can clamp one plate-type product, and when the plate-typeproducts are clamped, the to-be-polished side faces of the plate-type products are exposed outside. By means of the clamping device and the polishing method, multiple plate-type products can be clamped simultaneously; therefore, mechanical arms to which abrasive paper is attached can be utilized for polishing the side faces of the clamped plate-type products simultaneously, and the processing efficiency of polishing the side faces of the plate-type products is improved.