Due to the fast growth of building construction technology and increasing demands on the efficient use of land, human living space are expanded from on the surface to above and under the earth surface. It raises the need for three dimentional (3D) cadastral by realizing that the current cadastral system based on 2D is not appropriate to reflect the precise representation. 3D property unit is the basic unit of 3D cadastral similar to the parcel in 2D cadastral. Data source of 3D property units under the circumstance of 3D Cadastre is still a challenge. This paper provides the framework and the workflow of the conversion from CityGML to 3D cadastral. According to the requirement of the semantics and geometry of 3D cadastral objects, the mapping rule and correspondence between CityGML and 3D property unit will be calibrated. It is needed to extract the geometry data from CityGML for the construction of 3D volumetric units for 3D properties based on the mapping rules. Furthermore, test cases are implemented to validate the conversion method.