Calcium silicate is the main mineral of Portland cement clinker, in which low heat consumption and exhaust emissions require low calcium content.Therefore, exploring the presence of low calcium minerals will lay the foundation for the design and research of Portland cement clinker with energy-saving and low-emission.Using an efficient structure search method based on a particle swarm optimization algorithm and experimental technique, we study the compositional and structural evolution of calcium silicate phase, i.e., probable existing mineral phase from combining calcium oxide with silica oxide, preparing condition and hydration properties of 3CaO·2SiO2 (C3S2).Our results show that five calcium silicate phases including C3S, C2S, C3S2, CS and CS2 are stable.C3S2, less concerned phase, forms under the temperature arranged from 1100℃to 1460℃and its hydraulic activity is low in the room temperature with the hydration productions containing C-S-H gel and Ca(OH)2.Under the condition of 3-day hydrothermal curing at 80℃, its compressive strength reaches 8.6MPa for 2×2×2 test block.