The invention discloses a mop dewatering device which comprises a motor (10), a supporting base (15), a connection support base (9), a round table (8), a mop rod clamping device, a mop head clamping device and a mop head clamping driving device. The mop head clamping driving device comprises a pressing block (7), a gear (5) and an elastic piece (6), one end of the pressing block (7) is fixedly connected with the mop head clamping device in the vertical direction, the side wall of the other end of the pressing block (7) is an inclined face (4), the gear (5) is rotationally connected to the round table (8), one end of the elastic piece (6) is hinged to the round table (8), the other end of the elastic piece (6) is in clamped connection with a gear groove of the gear (5), and the inclined face (4) is a gear face meshed with the gear (5). By the adoption of the structure, work noise is greatly lowered, a mop can be wrung drier, and the ground can be cleaned more conveniently. Besides, meshing transmission of the gear inclined face on the pressing block and the gear is adopted in the mop head clamping driving device, the structure is simple, and operation is convenient.