Bowing phenomenon in the biaxially oriented film may reduce productivity due to aberration and fliaoing edge in the printing process. In order to understand the bowing phenomenon in tentering process, the mathematical model has been developed by considering overall continuity equation and relevant momentum equation. Model are solved analytically employing lubrication approximation for the case of isothermal and constant Newtonian fluid. Velocity profile and stress of the film at tenter process are calculated with the model. Geometrical bowing depended on goemetrical structure of the tenter process and n-value which is closely related to the volume change during extensional flow process. Model has been evaluated by comparison between theoretical value and experimental value from Daelim Jounju BOPP plant with two types of polypropylene resins and two types of operation conditions. These comparisons show qualitative agreement of model predictions. It may be said that this model can be applied to other resins such as PET.