Abstract: The study on the rock association, metamorphism, deformation and isotopic geochronology shows that the Yushulazi Formation in Eastern Liaoning is a single terrigenous clastic iron formation with metamorphism of greenschist facies. Its age belongs to Mesoproterozoic. The Yushulazi Formation underwent the tectonic deformation of Sibao Cycle during the period between the folding of the underlying Liaohe group and the sedimentation of overlying Yongning formation. The Yushulazi Formation, together with Yongning Formation, which quickly accumulated in the end of Sibao Cycle, formed the middle structural layer, making the three-layered structure of the crust in Eastern Liaoning region.