The elementary theory of optical information processing is reanalyzed by using wavelet theory in this paper. First, wavelet theory is used to reanalyze the Huygens-Fresnel principle, then an ideal of wave-front filtering is brought forward, the foundation of wavelet optics theory is thus established preliminarily. On the base of the theory, phenomenon of optical diffraction from a single slit, round aperture, grating, and so on are analyzed according to the ideal of wave-front filtering. The filtering in spatial domain, spatial frequency domain and a system of optical formatting imagines are also analyzed. The results show that it is feasible for the method of wavelet analysis to be used to study the problems of optical information processing, and it is more accordant with practical circumstances.