<p>Petroleum contaminated soil (PCS) has complex properties and compositions, which seriously endangers the environment and is difficult to treat. In this study, a new method for the remediation of PCS using MgO as remediation agent was proposed. Meanwhile, the mechanism of PCS remediation was revealed by various characterization methods. The study found that MgO was effective in remediating PCS. The results of PCS remediation showed that the residual oil rate of PCS decreased from 2.62 to 1.37%, and the absolute removal rate of oil in PCS after remediation was 37.3% under the optimum remediation conditions. The mechanism research indicated that the prepared MgO had large specific surface area, high hydration activity and strong adsorption with the conditions of calcination temperature of 650°C, calcination time of 120&#xa0;min and heating rate of 10°C/min. In the remediation process of PCS, MgO was tightly adsorbed on the surface of PCS particles, and the hydration reaction occurred rapidly after contact with water to form Mg(OH)₂. Mg(OH)₂ could effectively encapsulate soil particles firmly, ensuring the stability of PCS, thereby achieving the effective remediation of PCS. This study provided a new method for the remediation of low-concentration PCS, and had important scientific significance for the future research on the advanced treatment of low-concentration PCS.</p> Graphical abstract