In order to explore the thermal characteristics of a small nozzle flowmeter in the solid domain when transporting medium with different temperatures, the steady and transient thermal characteristics of each component of the nozzle flowmeter are calculated based on the finite element method. Results showed that the numerical calculation method could effectively reveal the internal thermal characteristics. When transporting high temperature medium, there was an obvious temperature stratification near the inner wall; when the inner wall temperature rose from 50 °C to 700 °C, the heat flow field at the inlet and outlet of the flowmeter increased significantly with the increase of temperature.