Abstract: Arsenic(As) is one of the common pollutants in contaminated sites, and it has strong carcinogenicity. Chemical washing is one of the commonly used remediation technologies for arsenic-contaminated soil, which could remove pollutants from soil in a short time. Although various washing agents have certain elution effects on arsenic-contaminated soils, single washing is difficult to meet the remediation requirements of heavily polluted soils. In order to study the multi-stage washing and remediation effect of different washing agents on arsenic-contaminated soil, a new green chelating washing agent methylglycine diacetic acid (MGDA) and a commonly used phosphate washing agent potassium dihydrogen phosphate (KH₂PO₄) were selected as the washing agents in this study. The indoor three-stage washing simulation experiment was carried out on the heavily arsenic polluted soil with a concentration of 891 mg·kg^-1 (solid-liquid ratio 1∶3). The As removal efficiencies of different washing agents and the changes chemical forms of As in the soil with or without washing agents were analyzed. The results showed that the removal efficiencies of As from soil by 0.12 mol·L^-1 MGDA reached up to 41.11%, which was significantly higher than that by 0.6 mol·L^-1 KH₂PO₄ (28.60%) and by the composite of 0.12 mol·L^-1MGDA and 0.6 mol·L^-1 KH₂PO₄ (10.88%-24.79%). MGDA has better removal efficiencies for aluminum-arsenic, calcium-arsenic and iron-arsenic; and KH₂PO₄ has better removal efficiencies for aluminum-arsenic and iron-arsenic. There were antagonistic effects between MGDA and KH₂PO₄ in the process of composite washing, and they are not suitable for composite washing.