The invention discloses an automatic balancing and lifting system for building outer wall cleaning and a control method thereof. The hardware equipment of the system comprises a fixed frame, a moving frame, a triangular stand, an extension spring, a roller screw mechanism and a balance weight on the roller screw mechanism, wherein the rear end of a roller screw of the roller screw mechanism is connected with an output shaft of a stepping motor through a coupling, and the front end of the roller screw is connected with a first bevel gear; a second bevel gear engaged with a first straight gear is fixed on a connecting shaft on a rack installation seat, the second bevel gear is engaged with the first bevel gear, a rack engaged with the first straight gear is installed below the first straight gear, and the front end of the rack is connected with the moving frame. The software control of the system comprises a computer system for executing inclined angle setting and distance detection of the system. The automatic balancing and lifting system has simple and novel structure, the cleaning performance and the like can be regulated according to the structures of wall surfaces and the requirements for the cleanliness of the wall surfaces, and thus, the cleaning of different conditions of wall surfaces can be realized.