The invention discloses a vehicle-mounted low-temperature heat insulation gas cylinder, and belongs to the technical field of low-temperature liquid storage and transportation. The gas cylinder comprises an outer shell, an inner container, a liquid level meter, a support, a front support outer tube assembly, a rear support outer tube assembly, a vibration reduction structure and a center frame body; the inner container adopts a flat long structure, the heat insulation layer wraps around the outer side of the inner container, the outer shell and the inner container are fixedly connected throughthe front support outer tube assembly and the rear support outer tube assembly, and a cavity between the inner container and the outer shell is filled with a foaming heat-insulating material after vacuumizing; the vibration reduction structure is vibration reduction plates each provided with a plurality of swinging-down holes; and the two ends of the center frame body are fixedly connected to the inner container, and a small hole is formed in the lower portion of the center frame body so that the aim of preventing overcharge can be achieved. According to the gas cylinder, the outer shell andthe inner container are designed into a flat long structure, so that the occupied space of the gas cylinder is reduced, in the transportation process, the vibration reduction effect of the vibrationreduction structure is good, and the safety is improved, the gas cylinder has the advantages that the structure is reliable, the processing is convenient, the utilization rate of automobile space is improved, and the transportation efficiency is improved.