In order to analyze the changing rules of temperature and pressure of the gas-liquid coupled field of LPG (Liquefied Petroleum Gas) tank under fire, the application of the wavelet finite element method on it is studied in depth. First, the research achievements of thermodynamics response of the LPG tank under fire and the wavelet finite element theory is summarized. Second the temperature-pressure gas-liquid coupled field mathematical model of LPG tank under fire is established based on the gas-liquid coupled theory and the wavelet finite element theory. Finally, the simulation analysis of the temperature-pressure gas-liquid coupled field in LPG tank under inject flame fire is carried out by the wavelet finite element method, ANSYS software and experimental test respectively, and results show that the wavelet finite element method has higher calculating efficient and precision in analyzing the temperature-pressure gas-liquid coupled field in LPG tank under fire.