Abstract: In view of the effect of filling on floor deformation, based on the solution procedure of foundation plastic deformation area boundary equation, we propose the boundary equation of plastic zone during filling or without filling, and determine the scope of plastic zone. Combined with case analysis, we compared the size of floor plastic zone during filling or without filling, researched the influence of filling on floor deformation, and got that filling reduced the plastic zone of pillar bottom. To better using strip filling mining technology, it provided a theoretical basis for guiding the rational distribution of floor roadway and maintenance, increasing the rate of coal mining, reducing coal mine safety accidents.