Abstract: Domestic LNG terminals usually use the model that a seawater pump with rated flow operation provides seawater for a single open rack vaporizer (ORV) to gasify LNG. Due to higher seawater temperature and lower natural gas flow of external input, the required seawater flow of ORV is less than the rated flow of seawater pump during non-winter operation. Therefore, this operation model is associated with excess energy consumption. Meanwhile, since the pressure range of natural gas pressure of external input is wide and the high-pressure pump can only provide the rated outlet pressure, so the outlet pressure of the high-pressure pump will be excessive when the pressure of natural gas of external input is lower, and resulting in excess energy. In order to solve the excess energy consumption problem of seawater pump and high-pressure pump, this paper started to explore its frequency energy-saving. Firstly, necessity of seawater pump and high-pressure pump frequency was analyzed. Secondly, in seawater pump, for example, outlet pressure and motor power of power frequency was calculated based on its characteristic curve. Then motor power of variable frequency was determined with the dichotomy and the similarity theory of pump. Thirdly, error analysis of power frequency was made on the seawater pump and high-pressure pump, showing the maximum relative error is 3.5%. Finally, through the comparison of the energy consumption, the seawater pump with variable frequency could save energy by 39.41% per annum, while the high-pressure pump with variable frequency could save energy by 47.39% per annum. Furthermore, economic cost of approximate 4.26 million yuan in LNG Terminal could be saved with variable frequency seawater pump and high-pressure pump per annum.