The utility model relates to a tower foundation of a power transmission line field is to current tower foundation of a power transmission line at mountain area transportation and exist economically not enough and a telescopic foundation structure of little load in mountain area who provides. Including pre -buried at the below ground the sleeve shaft and expand at the end with the lower part of sleeve shaft integral type structure, the lower extreme that the end is located the sleeve shaft is expanded to the lower part, the holistic orthographic projection face in the end is expanded for circular structure in the lower part, the upper end diameter that the end is expanded to the lower part will be less than the lower extreme diameter, is equipped with power supply line pole male hole groove in the sleeve shaft. The utility model discloses the design of oblique stock can improve the anti overturning stability in pole basis, is less than the lower extreme diameter with the base bottom design for the upper end diameter, and the messenger not only can improve on the basis the anti overturning stability in pole basis, can effectively improve anti - pulling capacity moreover, makes this basis be fit for telescopic foundation structure of little load in mountain area.