The image formulas of volume holographic system have been derived. The formulas are also suitable for the system which possesses a plane wave as a reference beam. The more exact calculation results can be obtained if these formulas are used in solving the image coordinate values of volume holographic system. The fomulas of the lateral, longitudinal and angular magnifications are given. The relations between the coordinate values of the object, image point, ratio of wavelengths μ and the image magnifications are proved in this papaer.