The invention relates to a novel U-shaped beam erecting device comprising gantry cranes, a triangular type crawler belt transmission system, connection rods and expansion and retraction devices. Each gantry crane comprises a beam transporting trolley, rigid support legs, a main beam, main beam connecting beams, on-beam trolleys, an auxiliary hook and a cab. The triangular type crawler belt transmission system is composed of hydraulic systems, hydraulic cylinders and crawler belt wheels. Each crawler belt wheel is composed of gears, a chain, a bearing, a structure shaft and a crawler belt. All the devices are made of profile steel and steel plates through welding. All the connection devices are plug pins or bolts. The two well-installed gantry cranes are connected with the triangular type crawler belt transmission system, all the connection rods and the expansion and retraction devices, and finally the novel U-shaped beam erecting device can be obtained. The novel U-shaped beam erecting device has the beneficial effects that by the adoption of the triangular type crawler belt transmission system, an operation rail of the gantry cranes does not need to be paved, the work efficiency is improved, and cost is reduced.