An in-situ thermal desorption system, an in-situ thermal desorption-oxidation remediation system and a remediation method are provided, wherein the in-situ thermal desorption system comprises a heating device and an extraction device, wherein the heating device is used for transporting heated air to the contaminated soil to desorb the organic pollutants, and wherein the extraction device is used for sucking the desorbed organic pollutants. The in-situ thermal desorption-oxidation remediation system adds a thermal catalytic oxidation device based on the in-situ thermal desorption system, wherein the organic pollutants extracted by the extraction device are catalytically degraded in the thermal catalytic oxidation device, and a device for recycling and reprocessing an exhaust gas is further added. The present disclosure also provides an in-situ thermal desorption-oxidation remediation method. The heating method of the present disclosure is novel, which reduces the cost of thermal desorption, strengthens the heating area, improves the heating efficiency, further enhances the thermal catalytic oxidation efficiency, and achieves the reuse and recycle of the exhaust gas. Thus, no secondary exhaust gas is produced.