Excavated foundation of transmission line have been used in mountain weathered soft rock, including column excavated pile model, jar shape embedded model and belled shaft digged model. Field prototype tests of 17 group different models have been carried out for highly weathered argillaceous sandstone. The foundation load bearing characteristics and failure pattern are analyzed based on test data. Load displacement curves show that the distributions are linear for shallow foundation, but the distributions are slowly varying for deep foundation. Based on the surface displacement variation rules, the characterization of foundation overall damaging reflect the significant surface fracture, and the foundation and its surrounding soil are pulled out. The foundation rupture angle reduces quickly with the increasing of foundation depth. But the rupture angle remains constant when the foundation reach a certain depth. By calculation of the test data, the rock equivalent ultimate shear strength of weathered soft rock is 32 kPa. According to the ultimate uplift capacity of unit concrete volume, the economical benefit of the belled shaft digged model foundation is remarkable.