The invention provides a filling method for an underhand sublevel drift mining underground mined-out area, and relates to an improvement of the filling method of underground mined-out area in the process of underground mining mineral resources. The filling method for the underhand sublevel drift mining underground mined-out area is characterized in that mine beneficiation full tailings are used asaggregate and portland cement is used as a cementing agent to prepare into filling slurry, and the filling slurry is transported to the underground mined-out area by pipeline self-flow. According tothe filling method for the underhand sublevel drift mining underground mined-out area, the slurry filled in the mined-out area has the characteristics of high dehydration speed, high early strength, good filling body integrity, stable pipeline transportation and the like, the full tailings can be used effectively, and the filling cost is low; and it is guaranteed that the filling body which is used as working top plate can meet the quality and strength requirements of a technical standard in the downward filling mining by a mold bag type filling method which uses the full tailings as the filling aggregate and filling technology with filling slurry pressure-relief. The whole tailings can be effectively utilized, the discharge of tailings waste to the earth surface is reduced, the environmental pollution is reduced, and the filling cost is greatly reduced.