Calcium silicate hydrate mineral was synthesized by carbide slag and silica white and was crystallized by taking calcium silicate hydrate mineral as crystal, and the effect of different Ca/Si molar ratios on calcium silicate hydrate mineral and the structure of phosphorus crystallization product was examined. Research showed that the difference of Ca/Si molar ratios had big influence on calcium silicate hydrate mineral and phosphorus crystallization products, that with Ca/Si molar ratio of 1.75:1, main phosphorus crystallization products were hydroxyapatite crystals with abnormal crystal form after synthesized hydroxyapatite reacted with phosphate, however, phosphorus crystallization products under other types of Ca/Si molar ratios were calcium phosphate with different forms, that different Ca/Si molar ratios led to the differences in crystallization level of calcium silicate hydrate mineral, whose reactive activity was affected and its Ca2+ and OH- releasing capacity was further affected, as a result, calcium phosphate and hydroxyapatite with different structures were obtained. Under the condition of Ca/Si molar ratio of 1.75:1, the synthesized hydroxy-calcium silicate hydrate mineral is mostly conducive to crystallization in the form of hydroxyapatite for phosphate recovery from wastewater.