The invention belongs to the field of application of agricultural and animal husbandry machinery, and relates to a square binder capable of performing union operation such as picking, pressing and binding on pastures or crop straws that are cut and aired in a grassland or a field. A key component of a bidirectional hinge traction device of the square binder consists of a V-shaped frame component, a pin shaft I, a bidirectional hinge piece, a pin shaft II and a traction beam solder; left and right lower hanging points of a tractor hanging device are respectively connected with the front end of the V-shaped frame component; the rear end of the V-shaped frame component is hinged to the front end of the bidirectional hinge piece through the pin shaft I; the rear end of the bidirectional hinge piece is hinged to the front end of the traction beam solder through the pin shaft II; the rear end of the traction beam solder is connected to a square binder frame body. The V-shaped frame component takes the pin shaft I as a center and can rotate left and right within a designed angle range; the bidirectional hinge piece takes the pin shaft II as a center and can rotate within the designed angle range. According to the bidirectional hinge traction device, the problem of interference between a cross beam and a transmission shaft of the tractor hanging device is solved.