X-ray phase imaging based on in-line Gabor holography is stuided. Using the theory of partial coherent X-ray in-line Gabor holography, we analyses both direct and indirect(holographic) phase imaging. The coherence has little effect on direct phase imaging. For phase holography, the effects of coherence, resolution of recording materiel, restoring length, and recording position on imaging quality are discussed. The uncertainty of recording position is the most important reason degraded the imaging quality. A requirement is given to get high quality phase imaging.