The invention relates to a high-pressure natural gas long pipe trailer for four-stage gas filling, belonging to the technical field of natural gas long pipe trailers. A set of gas inlet and outlet pipeline of a common long pipe trailer is divided into four sets of gas inlet and outlet pipelines. Each set of gas inlet and outlet pipeline comprises I-type serpentine pipes, bends, a three-way joint,thermometers, pressure gauges, a pressure gauge cutoff valve, II-type serpentine pipes, a four-way joint, a high-pressure five-way joint, nozzles, nuts, joints, NPT1 ball valves, double nipples, conical seal welding joints, an elbow, an NPT1 double nipple, an NPT1 gas inlet and outlet ball valve, a gas exhaust cutoff valve, a gas exhaust joint and a quick joint. A No.1 high-pressure gas cylinder and a No.2 high-pressure gas cylinder belong to a medium-pressure group, a No.3 high-pressure gas cylinder and a No.4 high-pressure gas cylinder belong to a low-pressure group, a No.5 high-pressure gas cylinder and a No.6 high-pressure gas cylinder belong to a medium-to-low-pressure group, and a No.7 high-pressure gas cylinder and a No.8 high-pressure gas cylinder belong to a high-pressure group. The NPT1 ball valves are installed among the groups. The high-pressure natural gas long pipe trailer for four-stage gas filling has the advantages that the functions of natural gas storage, transportation and filling are successfully integrated into one body, and the function of filling gas to the outside under no power is realized.