Crystalline-layered sodium silicate (δ-Na₂Si₂O₅) was prepared using amorphous sodium silicate as the starting material. The role of water in the hydration reaction of the solid phase transition at a high temperature was investigated. The commercial synthetic method for the layered sodium silicate was adopted dehydration method during phase transition from a sodium silicate solution. The new method was used for the hydration method during phase transition from a sodium silicate powder. XRD, TG/DTA, ²⁹Si MAS NMR, and FT-IR analyses were carried out to compare the role of water in the phase transition and identify of the silicate structure. It was found that two types of hydroxyl group (α-,β-OH) existed during dehydration in a solid phase transition caused by excess water. One type of hydroxyl group (α-OH) in the course of hydration from a sodium silicate powder existed due to a condensation reaction at a high temperature solid phase transition. The product prepared by the proposed method showed a high Ca²⁺/g and 98 mg Mg²⁺/g. A well-developed layered structure was also observed by the SEM analysis.