Abstract: In the report, the finite element software was used to construct a three-dimensional numerical model and study the development and distribution of the wall temperature field of frozen tundra with variable diameter. The numerical calculation results showed that the ultimate thickness of the permafrost in the strong and weak zones of 30 d to 40 d is 0.5 m. The minimum radius of the weak zone is 0.03 m, which makes the thickness of the permafrost reach 0.5 m. The thickness of permafrost at the junction of strong and weak areas is not affected by the strong and weak areas, and the thickness of permafrost is kept at 0.5 m. The results can provide theoretical basis for similar engineering design in the future.