A new synchronous multi-channel phase-shifting holography, which is suitable for dynamic imaging of three-dimensional (3D) objects, is proposed by analyzing the theory of phase-shifting digital holography. The reference beam, which has continuous 90-degree phase delay on the free space, interferes with optical field of laser diffraction through object. Multi-frame holograms are taken by using the balanced detector system which is comprised of four cameras. The information of 3D object is reconstructed based on Fresnel and Fourier optical principles. Simulation and experimental results show that single-shot phase-shifting digital holography has been achieved, synchronous multi-channel can be used for real-time measurement of dynamic objects, a large number of simultaneous multi-frame images improve the quality of the image.