The invention is suitable for leveling survey in topography, and relates to an automatic smoothening leveling ruler. The leveling ruler is composed of parts such as a ruler body (1), a circular level (2), a camera (3), a maincenter control center (4), a transmission system (5), a rotation shaft (6) and a ruler pad (7). According to the invention, the circular level (2) can exactly measure a perpendicular condition of the leveling ruler, the camera (3) positioned above the circular level (2) can continually shoot the positions of air bubbles and send the shot photos to the maincenter control center (4) through a transfer system for judgment so as to send out corresponding instructions; and the rotation shaft (6) is adjusted according to the instruction, the position change of the air bubbles of the circular level (2) is introduced until the photos sent back by the camera (3) show that the air bubbles are in the center, and then the leveling ruler is perpendicular. The leveling ruler strengthens the perpendicular precision of the leveling ruler, the perpendicularity of a standing ruler is guaranteed, a measuring error is reduced, and meanwhile, the operation is simpler.