The invention relates to an automatic washing and dewatering combined device of a rotary type mop, which comprises the rotary type mop and a washing and dewatering barrel, wherein the washing and dewatering barrel contains a barrel body, a dewatering basket and a lifting and fixing device of the dewatering basket, the lower part of the barrel body is provided with a washing area, the upper part of the barrel body is provided with a dewatering area, and the dewatering basket is arranged in the barrel body; the lifting and fixing device of the dewatering basket is arranged in the barrel body and is also connected with the dewatering basket, and the dewatering basket rotates around a main shaft of the lifting and fixing device of the dewatering basket; when the mop is washed, the dewatering basket is positioned in the washing area at the lower part of the barrel body; and when the mop is dewatered, the dewatering basket is lifted into the dewatering area at the upper part of the barrel body by the lifting and fixing device of the dewatering basket. By the device, the functions of washing and dewatering are integrated according to the design of human body mechanics. The device has the characteristics of small washing and dewatering volume, simple and scientific structure, small water consumption, low manufacturing cost, safe and convenient operation, strong practicability, attractive appearance and the like, and the time and the labor are saved.