Abstract: The structure of collapsible loess weakens in the process of soaking, thus the collapse deformation develops rapidly, the collapsibility deformation is also large and the strength significantly decreases. When the construction is in the collapsible loess areas, the foundation must be processed. By analyzing the collapsible mechanism and influencing factors of the loess, the humidification dynamic compaction method in processing collapsible loess foundation is suggested. As the theoretical basis for the mechanism of loess strengthening of the humidification dynamic compaction method, the method is applied to practice engineering. By the test for detection, the reinforcement effect is found to be better. The loess collapsibility is eliminated and the strength of loess is improved. The method is a suitable technology for ground treatment in loess area.