Abstract: Rotary digging pile has been widely used in transportation industry and construction industry due to its unique advantages of environmental protection, high efficiency, low cost and high degree of automation. However, the construction of rotary drilling rig is difficult due to the high natural strength of strata rock mass in hard strata such as moderately weathered and slightly weathered bedrock. The text researches the applicability of large diameter rotary digging pile in hard stratum. The results showed, the large-diameter rotary drilling pile with hole-forming by secondary hole-forming and local coring method is applicable in hard stratum. This technology is suitable for the hole-forming of rotary drilling pile with diameter greater than 800 mm in hard stratum such as medium-weathered and slightly-weathered strata. It is especially suitable for the case of insufficient power of rotary drilling rig or the torque of drill pipe exceeding the rated torque. At the same time, it also has a strong reference and guiding significance for the hole-forming construction of rotary drilling pile in dense gravel and boulder stratum.