The reflection wave of a cone beam, which is formed by a linearly polarized plane wave through a convergence system and then incident upon a stratified medium, is analyzed. The reflection phase shift in the whole aperture and the dispersion are figured out by using the expression of the electric field strength which is derived in the paper. Furthermore, aberrations can be discussed while the multilayer thin film is regarded as an element of an imaging system. In addition, an expression of the intensity distribution of the interference field produced by two reflection waves with the initial waves of SM (the electric vector is perpendicular to the plane of main ray incidence) and PM (the electric vector is parallel to the plane of main ray incidence), is deduced. Specially applied to a multilayer composed of seventy-one layers, the numerical calculation conforms to experimental results quite well.