An improved donut filter (IDF) algorithm is proposed and evaluated to restra in the outliers in the ladar range images.First,a generalized noise simulation model of ladar range image is proposed based on the analysis of the composition of the noises in ladar range image,which takes the ground,objects,and detailed parts into account,a nd can simulate such noise disturbance as outliers, dropouts and internal noise as well.Secondly,an improved donut filter (IDF) algo rithm to suppress the noise is proposed.Different noise suppression algorithms,such as median filter and improved donut filter,are analy zed by means of the simulation model and the results are also discussed from the points of the entirety,no outliers and detai led parts.Their capabilities in suppressing noise and protecting the detailed information are evaluated as well.Finally,the improved donut filte r algorithm is verified by analyzing the measured data. The results show that the capabilities of different noise suppression algorithms can be evaluated effectively based on the proposed simulation model and by means of mathematical analysis.Meanwhile,the correctio n coefficient of the improved donut filter can be obtained based on the target features,which can improve the capability of suppre ssing noise and protect the detailed information.