The purpose of this study that is carried out for the first time is to determine optimal thickness of WC-Co spray coating by HVOF (High Velocity Oxy Fuel) method on the surface of steel pinch-roll roller by utilizing finite element method. The pinch-roll was considered in this research is located at the end of the hot roll line of Mobarakeh Steel Company. The task of pinch-roll is to get and guide sheets toward the mandrel. The working environment of these components is acidic and they work in temperature and humid ambient. The surface of these rollers is worn and destroyed due to impact and movement of sheet on it. Because of micro-level deformation on the surface of pinch-roll, roller surface was necessary to be meshed by micron size element thus computational modeling would be complex and difficult. At the first, the relevant finite element model was optimized. After studying various techniques, eventually a two-dimensional model was considered in which the sheet and pinch-roll were supposed to be deformable with micron element size meshed surface. Also in order to optimize and reduce the time and cost of solving, only a 60 degrees sector of pinch-roll was modeled and a mass scale 100 applied for the pinch-roll. Then the critical condition of pinch-roll was determined. The Results showed that working condition of the pinch-roll at the initial impact is worse than other working times. Also, hard and thin sheets due to the higher speed at the hit movement to pinch-roll make the condition more critical. Surface damage created on the pinch-roll roller in the real state, was well shown by the finite element model. Finally, by defining two materials for the roller, coating was deposited on the pinch-roll in finite element models and the distribution of stress and deformation were obtained. Carbide Tungsten Cobalt (WC-Co) coating was used that by HVOF method was sprayed on the surface of pinch-roll.This cermet is extremely wear resistance and it is used for machining applications. The connection between the coating and substrate in thermal spraying methods, mostly is made by mechanical locks which have rather low strength. Maximum shear stress happens in the interface and since it is more than adhesion strength lead to delamination and failed coating on the substrate surface. Analyses showed although coating greatly improves the surface properties, the initial impact of sheet to the roller can cause deformation and failure of coating, as well as shear stress generated in the interface would be much more than strength adhesion coating to substrate. Among the various modes studied, the best thickness of coating was about 600 microns that causes minimum shear stress distribution both in the surface coating and in the interface of coating/substrate. Key words: Pinch-roll, HVOF, Finite Element Method, Shear stress, coating, interface of coating/substrate