The invention discloses a flattening device for asphalt road construction and relates to the technical field of asphalt flattening devices. The flattening device is mainly used for solving the problems that the flattening effect is poor and the flattening device is unsuitable for being used at night. The flattening device comprises a hinging arm, a device body, supporting legs, a second hydraulic cylinder and a motor, the upper part of the left side of the device body is hinged to one end of the hinging arm, a pull ring is arranged at the other end of the hinging arm, the motor is arranged at the right end inside the device body, a rotating disc is arranged on the front side of the motor, the position, away from the circle center, of the rotating disc is hinged to one end of a first connecting rod, the other end of the first connecting rod is hinged to the upper end of a fourth connecting rod, a first hydraulic cylinder fixedly connected with the device body is arranged in the middle of the bottom of the device body, and a flattening plate is arranged below the first hydraulic cylinder. The asphalt road surface can be effectively flattened, through the flattening plate and a pressing roller, the flattening device can adapt to working at night, energy is saved, and the flattening device is suitable for being popularized.