Abstract: In order to improve additional value of using fly ash,many experiments had been carried out to improve the conventional acid-leaching and alkali dissolution process,and finally a technology called ‘dip in twice with one acid/unite two kinds of alkali’ was determined as the new technology of element leaching in fly ash′s utilization.This technology consisted of four steps,namely,acid leaching,alkali dissolution,roasting,and second acid leaching.Maximum utilization rates of Si,Al,and Fe could reach 97.07%,86.67%,and 96.54% respectively.Polyaluminium ferric chloride (PAFC) product met the relative requirement  of standardⅡ of polyaluminium chloride in GB 15892—2003,the best dosing quantity was determined as 25 mg/L,and its wider applicable range of pH was verified.Quality of silica No.1 was better than the requirement of National Standard of Precipitated Silica (HG/T 3061—1999),and quality of silica No.2 met the requirement of the Standard.Analysis results by X-ray diffraction (XRD) and scanning electron microscope (SEM) were identical,namely,silica No.1 and silica No.2 were both made up of disordered noncrystalline state materials.Economic benefit analysis indicated that it could obtain 2 059.51 yuan net profit by utilizing 1 t fly ash.Therefore,it has good economic benefit. 