According to the transmission line geological condition, which is the weather rock with a thin surface of clay covered in hilly area, an environmental friendly composite foundation combined with digging foundation and rock bolt foundation had been proposed. The applicable scope of the composite foundation was demarcated, its advantages were expatiated, as well as some proposals concerning its further development and application were put forward. At last, the real model tests of two pilot projects were carried out to obtain the value of the efficiency factor of bearing capacity, which could provide reference for the application of the composite foundation in transmission line projects.