In this study, calcium oxalate chemically bonded material (COCM) was fabricated through the reaction between calcium oxide-rich blast furnace slag and oxalic acid (OA) at room temperature. The effects of the mass ratios of oxalic acid to blast furnace slag (BFS) on the mechanical properties of COCM were studied, and its solidification effect for heavy metals (Pb, Cd and Cu) was further investigated. The results show that the COCM with an OA/BFS mass ratio of 0.25 has the best mechanical property. The compressive strength at 3 d, 7 d and 28 d reaches 25.70 MPa, 27.86 MPa and 34.79 MPa, respectively. XRD and SEM were used to analyze the phase composition and microstructure of COCM. The results indicate that COCM is mainly composed of calcium oxalate (CaC2O4·H2O) and has tense microstructure. When the mass fraction of heavy metals (Pb and Cu) is 8%, COCM still has good solidification effect on heavy metals (Pb and Cu), and the toxic concentration of solid leaching is lower than the national standard limit. The results provide reference for preparing COCM from blast furnace slag.