Abstract: The chemical oxidation is a widely used remediation technology for petroleum hydrocarbon-contaminated soils. However, the effects of in-situ chemical oxidation on the geotechnical properties of contaminated soils are unclear. An in-situ jet grouting-aided chemical oxidation test is conducted at a petroleum hydrocarbon-contaminated site located at the lower reaches of the Yangtze River. The effects of petroleum hydrocarbon-contamination and chemical oxidation on the geotechnical properties of the studied silty clay are investigated, and the corresponding degrees of effects (DOEs) of series geotechnical parameters are evaluated as per China GB 50021-2001. The test results show that the DOEs of petroleum hydrocarbon-contamination (720 mg/kg) on the hydraulic conductivity are moderate. The DOEs of sodium hydroxide-activated sodium persulfate addition (3%) on the dry density are moderate, and those on the water content, void ratio, Atterberg limits, compressibility and hydraulic conductivity are significant. The compression indexes and the liquid limits of clean, contaminated, and treated soils exhibit a linear relationship. Furthermore, a positive correlation relationship is observed between the hydraulic conductivity and the void ratio of the clean and contaminated soils on the semilogarithm coordinate.