The invention provides a building outer wall spraying robot and a control method thereof, and relates to the technical field of building robots. The building outer wall spraying robot comprises a machine frame, a material storage box and a spraying machine, wherein the material storage box and the spraying machine are arranged on the machine frame, a spraying gun of the spraying machine is provided with a rotating mechanism capable of changing a spraying direction, and the spraying gun is fixed on a horizontal moving device capable of sliding in the horizontal direction of the machine frame; and the machine frame is provided with a lifting mechanism for enabling the machine frame to move in the direction of a plumb bob, and a stability maintaining mechanism for adjusting the movement stability of the machine frame, an outer wall recognition device for identifying a spraying region is further arranged on the machine frame, and the outer wall recognition device, the rotating mechanism, the horizontal moving device and the lifting mechanism are electrically connected to a controller. According to the robot and the method, the problems that in the prior art, manual building outer wallspraying is dangerous, the efficiency is low, and the spraying quality is not stable are solved.