Coal ?y ash from coal-fired power stations in Vietnam, which can cause serious environmental problems if managed improperly, is a promising silicon source for zeolite synthesis. This paper investigated the effects of ultrasound (UTS) energy on the extraction of silicon from the coal fly ash produced by the Duyen Hai thermal power plant using a 20-kHz probe immersed in the reaction mixture. Silicon was extracted from the ?y ash in an alkaline solution at different temperatures, times, and ultrasonic powers. The second-order design, or the central composite design, was employed to investigate the effect of each parameter on silicon extraction. Data analysis was performed by Response Surface Methodology (RSM) using Design Expert software. With ultrasound assistance, the efficiency of silicon extraction reached 65.92 %, which is a very high extraction efficiency considering the short extraction time and lack of fusion step. With the use of ultrasound, the extraction efficiency is significantly increased compared to the fusion method. The optimal region predicted from the empirical modeling is around the center point (90 °C, 50 min, 50 % amplitude).