<p>The objective of this study was to compare the washing effects of sulfuric acid (SA), citric acid (CA), ethylenediaminetetraacetic acid disodium (EDTA-2Na) and deionized water (DI Water) on the complex heavy metal-contaminated soil. The effects of washing agents concentration, liquid-solid (L/S) ratios and washing time on the types of heavy metals in the washed soil and their removal efficiency were studied. Meanwhile, the X-ray diffraction, Scanning electron microscopy and Fourier transform infrared spectroscopy were used to study the chemical properties, microscopic properties and element content of the washed soil. The results show that EDTA-2Na had a better washing effect than CA, SA, and DI Water for most heavy metal elements. As the EDTA-2Na concentration increased, the heavy metals removal efficiency increased. The optimal L/S ratio and washing time were 4:1 and 4&#xa0;h respectively for most heavy metal elements. Microscopic analysis displayed that the primary minerals in the contaminated soil were quartz, albite, potassium feldspar and fuchsite. The peak intensity of mineral crystallization in the contaminated soil decreased after washing, and EDTA-2Na had the strongest ability to dissolve minerals in the soil. The presence of fuchsite in polluted soil is the chief reason for the low removal efficiency of Cr. The washing agent concentration, washing time and L/S ratio should be carefully controlled to minimize the availability and fluidity of residual heavy metals in the contaminated soil when projecting soil washing for the remediation of composite heavy metal-contaminated soil.</p>