The invention discloses a device special for auxiliary wall surface leveling decoration. The device comprises a box body. A handle is arranged at the bottom end of the box body, a displayer is arranged at one end of the box body and arranged above the handle, and a sonar transmitter and a sonar receiver are arranged at the other end of the box body; and a spray head is arranged on a plane between the sonar transmitter and the sonar receiver and provided with an electromagnetic valve, a box cover is arranged on one side of the box body, and an installation groove is formed in the top end of the box body and internally provided with a liquid storage tank. According to the device special for auxiliary wall surface leveling decoration, through the sonar transmitter and the sonar receiver, flatness of the wall surface can be subjected to accurate measuring and can be displayed on a displayer in an image mode after being converted through a signal converter, so that observation of an operator is facilitated; marking can be conducted on unsmooth wall surfaces through use of the spray head, so that leveling treatment of the later period is facilitated; and the overall structure is small and exquisite, and carrying and use of a user are facilitated.