For ease of utilization goaf point cloudy data collected by CMS, it is a necessary link to stream point cloudy data. In this paper, a method for point cloudy data thinning of goaf based on slicing was put forwarded. According to the principle of acquisition of goaf point cloudy data, the goaf was idealized treatment, slice distance threshold was determined by the relationship of scanning angle, scanning line spacing and scanning point horizontal distance. The point projection to the closest slice was fitted curve section, combined with the simplification of improved angular deviation method, and examples were given to demonstrate the validity of the method.excavation.