Abstract: Geological investigation shows that the middle segment of the Mohe over-thrust nappe system is a typical over-thrust model, which includes imbricated reversal faults, pressed sharp edge folds, reversal folds, thrust deformation zones, and barrier folds. The structural deformation is in the SSE direction. Recently, the isotope studies show that the activities of the Mohe over-thrust nappe system occurred during the period from the late Late Jurassic to the early Early Cretaceous. The nappe belt and the Mongolia-Okhotsk tectonic unit have the same orogenic period and the same dynamics background.