A research has been carried out on the arsenic removal from simulated arsenic containing wastewater by sodium arsenite solution with the pre-oxidation ferrous salt method adopted. Using hydrogen peroxide as its oxidant, an oxidization of As(Ⅲ) to As(Ⅴ) can be achieved, followed by the formation of iron arsenate with the addition of ferrous chloride. An investigation is to be conducted on the effects of reaction time, solution pH, reaction temperature and molar ratio of iron and arsenic on the formation of iron arsenate. The results show that the removal efficiency of arsenic by ferrous chloride reaches the highest point, i.e. 99.85%, with the reaction time being 2 h, the reaction temperature being 85 ℃, the pH value of the solution being 4, and the molar ratio of iron to arsenic being 2.2. An X-ray analysis shows that the precipitation product is to be iron arsenate, and SEM analysis shows that the precipitation is to be ferric arsenate slag with a diameter of about 5 micron.