Subsea tree is the key equipment for deep-sea oil and gas development. Tubing hanger is the core component of the subsea tree, and its heat transfer calculation is related to the safety of oil and gas flow in the later period. Based on the theory of heat transfer, the heat transfer governing equations and boundary conditions under the steady and unsteady conditions of the subsea tree were analyzed, and the specific heat capacity, thermal conductivity and convective heat transfer coefficient of mixed natural gas were calculated. A finite element model of the heat transfer of subsea tree tubing hanger was established by using the numerical heat transfer method, and the temperature field distribution of the tubing hangers during steady production and unsteady shutdown was numerically simulated. The steady state calculation results show that the temperature of the inner wall of the tubing hanger is symmetrically distributed about the X=0 cross section, the highest is 57 ℃, which is the temperature of the oil produced, and the lowest temperature appears at the top of the tubing hanger, which is 21.672 ℃; after 8 hours of shutdown, the temperature of the tubing hanger drops to 21.66 ℃; within 0.5 h of shutdown, the temperature drop range is the largest, and the temperature of the tubing hanger drops to 25 ℃, indicating that the heat exchange between the internal produced fluid and the tree body is intense at the initial shutdown stage; after 2 h, the temperature gradually approaches the seawater temperature and finally reaches a steady state.