Compressive sensing ghost imaging has made great progress in recent years because it has the characteristics of less number of samples.Aiming at optical field distribution change in ghost imaging,the propagation process of light field was analyzed.The size of the lens makes the diffraction effect more obvious.The facula superposition makes actual light field become fuzzy and deviate from the preset value.The light intensity spread function of the diffraction limited system was calculated and the preset light field was revised.However,the revised light field acting as observation matrix can still be reconstructed under the condition of mutual coherence.Experimental results indicate that the revised light field is similar to actual light field and observation matrix can reconstruct high-grade picture.So it is significant to revise preset light field by using light intensity spread function.