Vehicle Liquefied Natural Gas(LNG) tanks are widely used in transportation, but people are facing the problem of unable to monitor the liquid storage level of LNG tanks accurately and efficiently, and this has become a difficult problem for scholars at home and abroad to solve. An analysis method of LNG tank liquid storage based on vehicle random excitation was proposed, and a whole set of test platform was set up. Taking the LNG tank and a supporting spring system as the research object in the experiment, a 3 degree of freedom (3-DoF) vehicle vibration model of LNG tank was established, to research the regulation between the changing of liquid weight and the changing of inherent vibration frequency, and the correctness of theoretical analysis was verified by experimental data, then to calculate the weight of the liquid storage tank. The method is accurate in calculation and has a good prospect of popularization and application.