Abstract: : A model of aberrations for rainbow holographic images reconstructed by a white light strip source is given . The range of effective spectrum of each element of the strip source gives rise to the same vertical shift of the image point. The etfective centre wavelength of each element gives rise to axial chromatic dispersions of the image point. The formulae given the corresponding permitted image distance can be calculated. The model is helpful in disclosing the physical nature of achromaticity in rainbow holography, and has its practical significance in the selection of parameters in light-path design.