SEM shows that flowers-and-plants-like sodium carbonate exists on the surface of sodium silicate sand grains when hardened by carbon dioxide, baculiform sodium acetate exists not only on sand surface but also inside sodium silicate film when hardened by ester method. The strength of sodium silicate sand mainly depends on the point-bridge connecting strength of dewatered sodium silicate film. The performance of reclaimed sodium silicate sand is determined by the extent of which salinous crystal is eliminated and reasonableness of relevant technological methods.