Based on high-speed particle image velocimetry technology(PIV), the flow law of particle flow field and the phenomenon of particle separation in powder mortar body under disturbance were studied. In PIV test, the fine-grained soil layer distributed in the Yellow River Delta area is taken as the test graded soil sample. By analyzing the experimental results of particle image velocimetry (PIV) of slurry flow field changes and particle migration stress under disturbance, the theoretical model of fine particle separation flowing film under disturbance was established. The results show that with the increasing F disturbance, when F disturbance is greater than G, the lateral pores gradually increase and the sedimentary soil layer gradually liquefies. With the enhancement of artificial disturbance force, the slurry flow field structure observed by PIV forms a negative vortex zone between the rising direction of disturbance force and the free surface, which gradually expands with the main cycle and sinks from the upper part, forming a complete main cycle vortex structure. According to the streamline test of particle image velocimetry, the area formed by particle migration path presents a wide distribution at the top and narrow distribution at the bottom. Experimental analysis on particle size distribution, plastic liquid limit and compressibility shows that the disturbed soil presents layered deposition, with coarse particle size at the top and fine particle size at the bottom, which is the main reason for layered deposition after particle disturbance. Cohesion makes cohesive soil particles agglomerate and enrich in the process of disturbance and migration, and compressibility indicates that the change rule of soil structure in the process of flow is upward disturbance and downward consolidation. Through experimental phenomena and mechanical analysis, the theoretical analysis model of slurry membrane separation is established in this paper, which is in good agreement with PIV test results. It can effectively explain the flow field motion and particle separation law of fine-grained mortar under disturbance conditions, and provide theoretical basis for related projects.