In the LNG trade handover process, it is necessary to understand the composition of natural gas, determine the calorific value of natural gas, and ensure compliance with legal natural gas composition standards. The online LNG micro chromatography sampling and analysis system can help quickly determine whether nitrogen and other low-temperature gases are mixed in LNG. To adjust the composition of natural gas to meet legal standards, it can also be used as a mixing station for adding nitrogen to high calorific value natural gas to convert it into low calorific value natural gas.