The band-gap of one-dimensional complex-periodic holographic photonic crystals is calculated by using transfer matrix method. Aiming at the dichromate gelatin recording medium, band-gaps are found in this refractive medium structure, and the effects of the refractive index, refractive index modulation and thickness of the medium on the photonic gaps are discussed. When the light is shining, using calculating to find that the refractive index and refractive index modulation changes does not affect the position of the band-gap, the width of the band-gap decreases with the increase of the refractive index of the recording medium, and increases with the increase of the refractive index modulation. To get a good band-gap, the thickness of the recording medium is at least 8 μm.