In view of the blind design, large amount of filling and high cost of treatment in the room and pillar mining goaf, the partial filling design method of roof-uncontacted filling and pier column filling was put forward. Based on the characteristics of the rectangular coal pillar gradually peeled by weathering process and the accumulation of peeled bodies, the model of the rectangular coal pillar peeling in the room and pillar mining goaf was builded, and the maximum peeling depth of the rectangular coal pillar was calculated. Based on the collaborative bearing of coal pillar and backfill, the theoretical calculation formulas of backfill with roof-uncontacted filling and pier column filling were derived by using safety factor method for coal pillar ultimate strength. These formulas could guide the design of partial filling treatment of room pillar goaf and reduce the cost of goaf treatment greatly. The results showed that the design strength parameters (elastic modulus, uniaxial compressive strength) of the backfill were inversely proportional to the filling rate, so the elastic modulus and uniaxial compressive strength of the filling material could be increased to significantly reduce the filling volume in the goaf and the treatment cost.