The invention relates to a plumb-hanging device for construction measurement, which comprises a first supporting post, a second supporting post, an air cylinder unit, a rotating unit, a motor unit and a fixing unit, a base, rollers and a first support are arranged on the first supporting post, a first vertical rod, a second support, a first inclined rod, a first fixed frame and a second fixed frame are arranged on the second supporting post, the air cylinder unit comprises a first supporting plate, a third support, a second vertical rod, a second inclined rod, an air cylinder, a first push rod, a connecting rod and a second push rod, the rotating unit comprises a first rotating rod and a second rotating rod, the motor unit comprises a motor, an output shaft, first holders, a second holder, a fixed block, a connecting thread and a plumb, the fixing unit comprises a triangular block, positioning rods, third holders, springs and a horizontal rod, and the upper surface of the triangular block is fixedly connected with the lower surface of the second rotating rod. The plumb-hanging device can adjust the length of the connecting thread and the angles of the rotating rods according to requirement, and increases working efficiency.