It is a common understanding that soil mechanics and engineering properties have regional characteristics, but which parameters and functions can be used to characterize regional soil features is an unsolved essential problem. As the starting point of the theoretical study of regional soil characteristics, based on the classical theory of soil mechanics and soil dynamics and the actual data, this paper puts forward the related concept, principle, criterion and demonstration. Based on the classical constitutive model of soil, the concept of dual control parameter is proposed, which is a basis for the theoretical study of regional soil characteristics. The concept of regional soil characteristic function is put forward, its definition, connotation and extension are clarified, and the construction criteria including control, universality, completeness, in situ, consistency, operability and existence are put forward. For conventional sand and clay, the idea of using N–Vs characteristic function to characterize its regional soil characteristics is proposed, the construction method is given, and its principle is clarified. The existence of N–Vs characteristic function of sand and clay is proved by analyzing the distribution characteristics of N–Vs function relations in 77 regions of 17 countries of the world.