The effectS of the coherence of X-ray beams on the resolution of X-ray holograms are theoretically analyzed. The concluSion is that the temporal coherence length required for X-ray beams is a quadratic function of the resolution and the size of specimen in X-ray lensless Fourier transform holographyj and the temporal length required for X-ray beams is proportional to the square of the resolution in X-ray in line holography.