The unified frame based on sparse prior for optical and SAR(synthetic aperture radar)image resolution enhancement is studied. First,we define the sparse prior,analyze the relationship between the sparse prior and resolution enhancement,and explain by parameter estimation theory. Second we unify the observation model for both optical and SAR image.Thirdly we unify the prior description. Finally the unified object function is constructed for both optical and SAR images. The examples for both optical and SAR images are presented,in which the object function are based on the sparse prior in different data domain respectively.