Harmless treatment method of arsenic-containing waste reagent

The invention discloses a harmless treatment method of an arsenic-containing waste reagent, and belongs to the technical field of harmless treatment of highly toxic reagents of hazardous wastes. The method comprises the steps: dissolving the arsenic-containing waste reagent to obtain a first solution; fully reacting ferrous sulfate with first hydrogen peroxide to obtain a second solution; slowly adding the second solution into the first solution, and reacting to obtain a third solution; and adding calcium oxide, cement and gravel into the third solution. According to the method, a certain amount of ferrous sulfate, hydrogen peroxide and calcium oxide are added into the arsenic-containing waste reagent, so that As and Fe are respectively converted into As and Fe by the arsenic-containing waste reagent through oxidation-reduction and complexing co-precipitation reactions, arsenic-iron complex precipitates are generated, and the stabilizing effect of reducing the toxicity and mobility of the arse