To explore the characteristics and mechanism of encrustations formation on deteriorated stone relics,encrustations in the Longmen Grottoes of Loyang and on the sandstone foundation of the Xihuang Temple Tower,Beijing,were systematically analyzed and studied using chemical analysis and Xray diffraction (XRD).Results of thjs study show that the encrustations of the Longmen Grottoes are formed slowly after dissolution and precipitation of rock carbonates as a result of water leakage. The encrustations on the sandstone foundation of Xihuang Temple Tower are from masonry mortar (the main component is calcite).The white encrustation is formed after masonry mortar is dissolved by water,the solution flows，and calcite precipitates and recrystallizes on the surface of the sandstone.