Abstract: A method of deriving the imaginary part of a complex holographic function from its real part in acoustic holographic array imaging is given in this paper. By using the complex holographic function, combined this imaginary part with the known real part, it is possible to reconstruct the image of an object without a conjugate image. The condition of applying the method is that dimension of the object to be imaged must be less than or equal to λz/2d, λ-wavelength, d-interval between sampled points, z-distance between object and receiving plane. Simulation with a computer proves the validity of the present method.