Soil, one of the most important building materials, is being used even now. In the course of understanding and mastering the performances and characteristics of different environmental soils by human beings, a rich variety of earthen architectural sites have been created. Based on documentary records and research results, this paper divides earthen architectural sites into five classes (i.e., raw soil, wattle and daub, rammed earth, adobe masonry and mud piled construction) and 15 subclasses by building technique on the basis of the investigation of preservation state, architectural form and structural feature of earthen sites and traditional building techniques. It also reveals that 1) the building techniques show a progressive developing evolution with the promotion by productivity growth and functional requirements, and 2) different building techniques have their respective features but interpenetrate to each other, which indicates building techniques are the embodiment of acclimatization and functional requirements and have certain regularity. This paper provides a basis for further study of early architectural forms and building techniques.