The scattering problem from the curvilinear surfaces is introduced by the method of Modified Theory of Physical Optics (MTPO). The method is based on the physical optics (PO) current, on the scaterers' and aperture surfaces. The integral equation is achieved by these currents and the result is found with the stationary phase method and edge-point technique. MTPO can be applied to calculate not only the reflected fields but also to calculate edge diffraction fields of various surfaces. In this paper MTPO method is to be explained in addition to the solution of the scattering (reflection+ diffraction) problem on perfectly conducting (PEC) parabolic surface by this method. The comparison with cylindrical surface proves the validity of the solution. Since MTPO is an innovative method, there are so many problems for different geometries which can be solved by this method.