The forming of intensive Bragg diffraction maxima of recording of volume reflection holograms in dichromated gelatin (DCG) is investigated. The Bragg maxima up to 4-th order are received at use of special chemes of hologram recording. Mentioned maxima are located in the spectral range form UV up to IR wavelengths. The intensity of harmonics is high enough. By means of rigorous chain-matrix method the spectral characteristics of holographic structures with uniform on thickness parameters and non-sinusoidal refractive-index modulation profile are calculated. Spectral curves for various sets of hologram parameters are computed and approximation of spectra received experimentally is conducted.