Abstract: The BOG(Boil-Off Gas)process related to energy consumption and safe operation is one of the critical issues that should be considered at LNG filling station. Therefore, the model of BOG static calculation is established, taking the 1.5×10⁴ m³/d capacity of LNG filling station in Lanzhou as an example, a set of BOG re-liquefaction equipment(mainly including one liquid nitrogen tank, one BOG/liquid nitrogen exchanger, one LNG collection tank, a few pipeline and valve)which uses liquid nitrogen cooling capacity is designed to avoid energy dissipation and environmental pollution caused by BOG direct discharge. BOG re-liquefaction capacity of the equipment is theoretically calculated and its economical benefit is analyzed. The results show that the amount of BOG production is 322 kg/d, the mass ratio of BOG re-liquefaction capacity and liquid nitrogen consumption is 1:1.92, which provides the theoretical basis for the design of the test equipment. The total cost of static analysis of the BOG re-liquefaction equipment is 0.39 million yuan, the total profit before tax is 0.144 million yuan, and the net profit is 0.105 million yuan. Therefore, it has good economical benefit. Accordingly, the investment should be considered to BOG re-liquefaction equipment of LNG filling station.