To solve the problem of uniform temperature field distribution of the simulation system in the environment of underground extra-deep well, the system temperature field with large length-diameter ratio, large delay and many kinds of complex heat exchange mode were simulated numerically, and the effective uniform temperature distribution method was obtained. First, the components of simulation system and work principles are introduced. Then, heat transfer model of the system is given according to the heat transfer theory. At last, temperature field distribution status of the system is simulated, and compared with the actual heating curve, the effectiveness of simulation results is approved.