Abstract: The turbopump-fed rocket engine used for the upper stage has a complex structure, and always subjects to extreme thermal environment variations. The thermal control system is usually designed to ensure all components of the engine work in an appropriate temperature range. The knowledge of the heat transfer characteristics of the turbopump-fed rocket engine is crucial to the development of the engine. On the basis of analyzing the thermal environment of the engine, the thermal modeling method of the engine is proposed, and the thermal network method is employed to analyze the thermal environment characteristics of the engine. The accuracy of the thermal analysis method is evaluated by a comparison with the thermal balance test of the engine. After verification, the current thermal analysis model is used to analyze the thermal characteristics of the engine in the flight. The thermal analysis method developed in this paper can provide references for a further study of the thermal analysis of other turbopump-fed rocket engines.