The ground substrate is a new concept in the field of natural resources, proposed by Chinese scientists. Explaining and standardizing from a theoretical perspective is an urgent and significant issue that needs to be addressed at present. This article, based on the practices of multiple ground substrate investigation and research projects, clarifies the scientific connotation of ground substrate and its layer, as well as their differences and connections with related discipline terms through in- depth study and analysis. We comprehensively consider five factors: the depth of the underground temperate zone, the depth of crop and vegetation root systems, the depth of the surface karst development zone, the thickness of the weathering crust, and the burial depth of groundwater. Based on these factors, we define the bottom boundary of the ground substrate layer. This article proposes five three- level classification schemes for ground substrate and four basic types of ground substrate layer configuration division schemes based on the material type, genetic type, and characteristic physicochemical properties. Finally, we systemically summarize and sort out 20 indicators of ground substrate physical- chemical and microbial properties closely related to vegetation and crop growth. These indicators constitute the basic framework of ground substrate theory and can be used as a reference and basis for future ground substrate investigation and research.