Abstract: To analyze the mechanical properties of construction waste aggregate-coarse fly ash-based cement fillers, orthogonal test is used to determine the optimal proportion of cemented paste backfill, and uniaxial compression, triaxial compression test are carried out. The results show that the average elastic modulus of cemented paste backfill is 971 MPa, the average Poisson’s ratio is 0.028 99, the cohesion force is 0.932 MPa, and the internal friction angle is 41.23° on the 28 d, which indicates that the transverse deformation of the cemented paste backfill is small during the compression deformation process. The interior has a certain compaction deformation space. Through the conventional triaxial compression test of the specimen, it is shown that the cemented paste backfill shows obvious plastic strengthening characteristics under three-dimensional stress conditions.