The internal curing mortar was prepared by water-saturated hollow glass microspheres in this paper. The water release characteristics and shrinkage retardation effects of water-saturated hollow glass microspheres were studied. The role of internal curing water in cement hydration process was investigated, and the internal curing mechanism of water-saturated hollow glass microspheres was illustrated. The results show that the pore size on the surface of hollow glass microspheres is 1 ~ 20 μm. When the relative humidity is 97. 5% , the water release percentage of water-saturated hollow glass microspheres is greater than 95% . When the internal curing water is introduced through water-saturated hollow glass microspheres, autogenous shrinkage of internal curing mortar decreases gradually with the increase of internal curing water- binder ratio. The internal curing water can improve the relative humidity inside cement paste and the hydration degree of cement, and significantly extend the humidity saturation period of cement paste, so as to reduce the early autogenous shrinkage of concrete or mortar.