Abstract: This paper introduces the BOG (Boil Off Gas) properties of LNG, and the BOG calculation method under different conditions, as well as two BOG processing techniques, direct compression technique and re-condensation technique. Two processing techniques are compared quantitatively with Bernoulli Equation and checking computations with examples are made. The results show that under same working conditions, the re-condensation technique can save energy compared to direct compression technique, and the greater the BOG processing quantity is, the lower storage pressure of LNG storage tank is, and when the pressure of pipeline network is higher, then the energy saving effect is more obvious. The conclusion is that the re-condensation technique is applicable to the BOG processing of large-scale LNG terminal, and direct compression technique is applicable to small-sized LNG satellite station.