Abstract: To study the effect of supports and gob waste rock on the periodic fracture characteristics of the main roof in mechanized face with large mining height, the characteristic quantity of supporting effect is introduced, the mechanical model of roof rock beam is established, and the periodic fracture characteristics of basic roof are analyzed. The results show that the main roof periodic fracture interval increases with the increase of the thickness and tensile strength of main roof and the decrease of the load value under the same supporting condition; and main roof periodic fracture interval increases with the increase of the supporting strength and roof distance of the support and gob waste rock under the same mining condition. In combination with in-situ monitoring, the main roof periodic fracture feature was verified.