Abstract: A rapid and sensitive metnod for the determination of Ca and Al in water glass by AAS has ben develaped. The sample was dissolved in hydrofluoric acid and perchloric acid. Calibration curve of the method was lineal. Related coefficiet was 0.999. Lineal calibration range 0~4μg/mL (Ca) and 0~10μg/mL (Al). The satisfying results were abtained for the water glass determination of different plants. The velative standard deviations were 1.7~5.2% for Ca and 6.8-9.5% for Al and the recoveries were 100-105% for Ca and 90~103% for Al, respectively.