The invention provides a method for removing arsenic from heavy metal contaminated soil. The method comprises the steps that firstly, the arsenic contaminated soil is subjected to dissolution treatment after reinforcers, water and the heavy metal contaminated soil are mixed, so that dissolution filtrate is obtained; and secondly, an iron-based adsorbent is adopted for conducting adsorption on the dissolution filtrate. According to the method provided by the invention, intensified dissolution can be conducted on the arsenic in the heavy metal contaminated soil by adoption of the reinforcers, the subsequent adsorbent can be fast combined with dissolved arsenic, and the arsenic is adsorbed and removed; and the arsenic in the soil can be efficiently and thoroughly removed by combining the two processes of in-situ competitive releasing and ectopic adsorption in remediation, and secondary contamination is avoided. Results of the embodiment show that the arsenic removing rate can reach 27-31% if the arsenic-containing soil is treated according to the technical scheme provided by the invention.