In order to understand the characteristics and mechanism of the thermal process of liquor fermentation system, which have great significance to the temperature control of the fermentation process and the mechanization of the fermentation system. The temperature distribution of fermented grains and the soil surrounding the cylinder are compared in different seasons. The process of biological heat generation and diffusion during the Fen liquor fermentation was confirmed. The temperature variation characteristics of fermented grains and heat conduction is the main mode of heat transfer in fermentation is determined. The important influence of temperature on the thermal process of fermentation is discussed. The numerical simulation of the thermal process of the fermentation system has been realized by measuring the thermal physical parameters of the fermentation system and using the finite element method of partial differential equation, which lays a foundation for the detection and control of fermentation process. The change pattern of fermented grains temperature in fermentation process is the basic characteristics and requirements of liquor fermentation, research and production of liquor should meet.