The solid Ca2SiO4 is synthesized through solid-state reaction using analytical reagent CaSiO3 and CaO as raw materials. The conditions of melting reaction between Ca2SiO4 and NaOH are optimized through an orthogonal experimental method. The optimized experimental conditions are a reaction temperature of 873 K, a reaction time of 180 min, and an alkali to ore ratio of 6:1. Based on the optimized conditions, in situ detection for the melting reaction process between the Ca2SiO4 and NaOH is made by Raman spectroscopy analysis. Furthermore, an X-ray diffraction (XRD) and infrared spectrometer (IR) analysis are used to test the residue, which is separated from the post-reaction Ca2SiO4--NaOH melt after water leaching. The results show that the Si-O bond in the SiO44− is destroyed, and the Na+ inserts itself into the silicate lattice to produce an intermediate product, Na2CaSiO4, in the process of reaction. After the alkali melting reaction, Ca2+ can be fully separated from the SiO44− array structure and react with OH− in Ca2SiO4--NaOH melt to form Ca (OH)2.