Abstract: Once leakage occurs in the gas pipeline under high pressure, it is very easy to form jet fire in case of encountering open flame, which will pose a great threat to the safety of people and property around the pipeline. In order to study the combustion characteristics of outdoor high pressure natural gas jet fire, an outdoor horizontal high pressure natural gas jet fire experiment was conducted using a natural gas pipeline with diameter of 25 mm and operating pressure of 5.8 MPa based on the influence mechanism of natural gas jet fire. The results show that the flame will produce an angle of 11.3°±1.4° due to the buoyancy caused by high-temperature flame during the stable gas combustion. Besides, a jet flow not involved in combustion will be formed in the orifice of the leak hole during the jet combustion of natural gas, the gas flow in this area has a fast jet speed and not easy to burn, the average temperature in the center area of jet flame is higher than 1 000 ℃, and the highest temperature of the flame center is more than 1 300 ℃. The flame length is 19 m to 21 m, and the maximum thermal radiation is 20 kW/m² at the place 10 m away from the flame center. In general, the experimental results have reference value for the fire accident treatment and the determination of safe distance of high pressure natural gas pipelines.