Abstract: In order to solve the problem of insufficient supply of filling materials at goaf in some areas, in this paper, urban construction solid waste is used as raw material to process recycled aggregate, which is used to replace part of fly ash to make new filling slurry, and its physical and strength characteristics under different curing conditions were tested. The results show that the setting time of the new filling slurry meets the requirements of grouting. With the increase of the aggregate proportion, the stone rate of the slurry decreases and the fluidity increases. When the water-solid ratio is 1∶1.2 and the proportion of recycled aggregate replacing fly ash is below 50%, the stone rate and fluidity of the slurry are good; when the replacement ratio is more than 70%, the slurry has segregation phenomenon; the 28 d compressive strength of the two groups of slurry stones is much greater than 2 MPa, and the 90 day long-term strength value is 3.59 MPa at the minimum and 7.93 MPa at the maximum, in addition, the compressive strength of pure cement fly ash slurry stone body at each age is greater than that of other groups with recycled aggregate. Under the same ratio, the short-term compressive strength of the stone body under water curing is greater than that under standard curing. The high concentration slurry with water solid ratio of 1∶2 and 1∶3 has good physical properties, and the maximum long-term strength can reach 15.94 MPa. Combined with the research results, the optimization of slurry ratio under different goaf conditions was analyzed and discussed, and it was applied to the actual goaf filling treatment project.