Abstract: Structural modeling is the foundation of 3?D geological modeling for lithological reservoir. Establishing an accurate stratigraphic framework is the fundamental guarantee for reservoir facies model and attribute model development. The complexity of structure makes the structural modeling for complex fault?block reservoir more difficult than for traditional lithological reservoir. Combined with the feature of complex fault?block reservoir and conventional process of 3?D geological modeling, this paper presents Point?Line?Surface?Geometry four?step structural modeling technique and detailed operation procedure. In view of Youshashan reservoir characteristics in Qaidam basin, the 3?D structural model is developed for this complex fault?block reservoir by using the four?step structural modeling technique