Abstract: The geo-formation structure is an original impact factor for the stability and safety of geotechnical and geological engineering and also an important content of field survey. A geo-formation identification while drilling (GIWD) system is developed, and its operating principles as well as the basic units are illustrated. The drilling process is coded, and a real-time identification method for the geo-formation structure is established. Besides, the ranges of specific energy values in weathered rock and structural rock mass of soil layer/scattered, cracked and intack granite are determined. The classification standard of diamond drilling specific energy for geo-formation is formulated and verified by in-situ drilling tests. The specific energy values are 0.0017~0.6955 kN·m/cm³ for the soil layer and scattered structure, 0.0258~0.9798 kN·m/cm³ for the cracked rock and 0.0018~2.4935 kN·m/cm³ for the intack rock, respectively. The results show that the above approach agrees with the traditional investigation and can further be applied for real-time recognition of strata and geotechnical structure, and it may provide a new approach for geotechnical engineering survey.