In the active illumination intensity imaging method, the effect of coherence changes on the spectral modulus was considered. The model of the spatial coherence of the uplink coherent light field was established which the coherence factor was introduced on this basis. And the intensity correlation imaging model based on coherence change was established. The influence on spectral modulus of the intensity correlation imaging was simulated by coherence changes. The correctness of the model is verified by the design experiment. The peak signal to noise ratio of the spectral modulus of the proposed model and the original model is analyzed. According to the analysis results, it is necessary to introduce the coherence factor in active laser illumination; and the peak signal to noise ratio is improved by 3.6%~6.2% in different turbulence coherence length. The quality of the spectral modulus recovered by the proposed intensity correlation imaging model based on coherence change is better.