Copper slag based ferrous oxalate cement(CS-FOC) exhibits significant potential for applications in high temperature kiln repair and nuclear waste stabilization/solidification, owing to its rapid setting properties and high early-age strength. This study comprehensively investigates the evolution of properties, phase compositions, and structure of CS-FOC following exposure to elevated temperatures(150~1 000 ℃), building on prior research. The results show that CS-FOC achieves a compressive strength of 55.1 MPa after 28 days of natural curing, primarily composed of newly-formed ferrous oxalate dihydrate(FeC₂O₄·2H₂O) and unreacted fayalite(Fe₂SiO₄). Exposure to elevated temperatures induces regular changes in both the compressive strength and structural integrity of CS-FOC. At temperatures exceeding 250 ℃, FeC₂O₄·2H₂O decomposes into iron oxide, leading to structural degradation and a consequent reduction in strength. Despite this, the material maintains a stable compressive strength of about 15 MPa after exposure to temperatures as high as 1 000 ℃. These findings highlight the superior thermal stability of CS-FOC, alongside its ability to retain a relatively high compressive strength under extreme thermal conditions.