Abstract: Thermal overhead pipeline system is widely applicable for petrochemical and city heat supply engineering. As nonlinear factor of displacement is not taken into account in design of thermal overhead pipeline previously, actual stress condition of pipeline and support can't be reacted correctly. Now a mechanical model is given to show stress conditions of thermal overhead pipeline and support. Analyzes a load acted on thermal overhead pipeline and calculates pipeline's displacement using infinite element iteration method by means of combination with infinite element method and variable spring coefficient iteration method. Calculation result shows that nonlinear factor of displacement must be considered when analyzing thermal overhead pipeline and support's frictional force must be taken into account correctly at the same time.