Abstract: Study of the Nappe structure and fault- related folds in the western Daqing Mountains, Inner Mongolia, indicates that the Daqingshan tectonic system consists from south to north of the thrust nappe sheet zone at the root, inclined-overturned folds and thrust belt in the central part and fault-related fold belt in the front. The deformation intensity weakened form the root zone to the front zone. The typical fault bend folds and fault propagation folds are developed in the front belt. The nappe structure is NNW-vergent, formed mainly at the end of the Middle Jurassic, with a displacement of 10-20 km, and its formation is probably related to the closure of the Okhotsk Ocean in Yanshan phase.