Abstract: The comparative tests of removing silicate scale with alkalinedissolving and alkaline ultrasonicdissolving methods was carried out considering their merits of ultrasonic and chemical methods, and the feasibility and the optimal technical parameters of removing the silicate scale rapidly and safely at low temperature and normal atmosphere were examined at different conditions of alkaline andultrasonicalkaline methods. The results showed that the scaleremoving efficiency was only 24.05 % when using 15 % NaOH solution at 90 ℃ for 3 h. However, the scaleremoving efficiency reached to 60 % in 5 % NaOH solution at 90 ℃ for 1 h or in 10% NaOH solution at 80 ℃ for 1 h when combining with ultrasonic method. It was indicated that the dissolving rate of silicate scale in the ultrasonic solution was 4.01—9.45 times faster than that of in nonultrasonic solution. Therefore, silicate scale on disk disperser could be dissolved quickly, safely, cleanly and effectively by phonochemistry, the highest ratio of dissolving silicate scale was up to 63.27 %.