The invention discloses a valve inner cavity polishing device which comprises a case, a first motor, a polishing wheel, a second motor, an air cylinder and a valve clamping mechanism. The first motoris installed at the upper end of the case, and the polishing wheel is installed on a rotating shaft of the first motor. The second motor is installed at one end of the case, and a rotating shaft of the second motor extends to one end of the air cylinder. The valve clamping mechanism is composed of a bottom plate, connecting plates, fixed plates, screws, nuts and clamping plates. The valve inner cavity polishing device is high in automation degree and effectively improves the polishing efficiency of a valve inner cavity; in addition, polishing treatment of the valve inner cavity is carried outin the sealed case, so that the safety of operators is guaranteed; and moreover, waste generated in the polishing process cannot be scattered everywhere on a site, and the working environment is protected.