A new method for the removal of P, As, Si and Mo to obtain the purified solution of ammonium tungstate in one step by ion-exchange adsorption has been investigated. Adjusting the pH of raw sodium tungstate and converting the MoO 4 2− to MoS 4 2− fully at first, an ‘acid conditioning without harmful anions’ process for pH adjustment in solution is adopted. The solution is then adjusted to have the correct concentration of tungsten and pH-value. When the solution passes through the ion-exchange column, tungsten and molybdenum (in the form of arsenic) are adsorbed in resins together preferentially, the ions of P being unwanted. (As) · Si goes into the raffinate. Then, tungsten is desorbed preferentially from resin, by a mixed solution containing ammonium to separate molybdebum from tungsten. Lastly, we use alkaline sodium hypochlorite solution to oxidize and desorb molybdenum (arsenic) to regenerate resins.