To define the application range of simplified calculation method of soil heat absorption in the ventilation design of power cable tunnels and analyze its calculation deviation, heat transfer process is simulated with numerical threedimensional model. The deviation rate of tangential heat transfer  is defined to quantitatively assess the deviation between onedimensional heat transfer assumptions of the simplified calculation method and the actual heat transfer process, and the calculation deviation caused by simplified calculation method and its applicability are analyzed in the case of different obstructions on the tunnel′s inner surface. The results show that the maximum value can be up to 95% at the edge of the blocked area of tunnel inner wall. Since the blocked area of the lower part is greater than that of the upper part, the twodimensional character of soil heat transfer is observed, and the deviation reaches 57.5%. The heat transfer process in the upper part is similar to the onedimensional assumptions, and the deviation is only about 10%. Therefore, the current simplified calculation method for calculating the soil heat absorption in tunnels is mainly applicable to the upper chamber of the tunnel.