An incoherent self-interference digital holography imaging system based on Michelson interferometer was reported. The system recorded the holograms of USAF1951 resolution target, onion epidermal cell and herbaceous stem crosscut. Reconstructing the captured hologram by three-step generalized phase shift can effectively eliminate zero-order images and twin images, and obtain a high resolution reconstructed image. The element three in group nine on the USAF1951 resolution target can be clearly seen, with a resolution of 645 lp/mm. The effect of diffraction distance on the quality of reconstructed image was studied by analyzing the relationship between them. Moreover, a 3D image of the object can be obtained by this system through reconstruction of the hair hologram.