In this paper, the mechanical property changes of calcium aluminate cement (CAC)-based materials in soft water environments and the mechanisms influenced by temperature were studied. The compressive strength of CAC mortar was monitored, the phase composition and microstructure of the paste specimens were analysed by XRD, TG, EDTA titration and SEM. Results show that, the composition of CAC hydration products did not change significantly in 20℃ soft water environment, and the formation of a large number of amorphous phase AH3 in the paste ensured the stability of the long-term performance of the material. In the 60℃ environment, an increase in temperature triggers phase transitions, and the presence of soft water further enhanced this effect. Under the combined influence of temperature and soft water, the transformation of the crystal products and dissolution of some phases lead to disruption of the CAC paste microstructure and pore creation, resulting in degraded material properties.