Coherent diffractive imaging (CDI) is a lensless, high-resolution imaging method. In order to overcome the problems of poor-quality image and slow convergence of iterative algorithm in traditional CDI, here multimode fiber source is selected as the lighting source to replace the traditional plane-wave. A phase-only spatial light modulator (SLM) is used as a negative lens instead of a positive lens in a 4f imaging unit. The diffraction field can be rapidly changed at a very short distance so as to realize a fast convergence and then save a lot of iteration times. This proposed setup has advantages such as a simpler structure and static recording. Both simulations and visible-light experiments demonstrate the good imaging quality and robustness of this method.