Vaterite （a crystal form of calcium carbonate） was utilized as a substitute for limestone powder （mainly composed of calcite crystal form of calcium carbonate） in the preparation of cement paste and mortar specimens. The impact of crystal forms of calcium carbonate on the compressive strength and microstructure of cement mortar was investigated. Utilizing calorimetry and X-ray diffraction and other techniques for microscopic analysis， the interaction mechanism of vaterite and calcite were explored. The results indicate that vaterite exhibits a higher chemical reactivity compared to calcite， thereby enhancing the hydration rate of the system. The introduction of vaterite into the silicate-aluminate cementitious system induces a reaction between calcined kaolin tailings and calcium carbonate. The resultant hydration products， including calcium silicate（aluminate） hydrate（C-（A）-S-H） gel and hydrated calcium carbonate aluminate crystal compounds， cover the vaterite surface and bind with the cement matrix， refining the pore structure and significantly improving the compressive strength of mortar.