This study addresses the significant concern of contaminated soil resulting from oil leakage and explores the influence of indirect heated microwave thermal desorption technology on geotechnical properties. Geotechnical engineers increasingly worry about the repercussions of hydrocarbon-induced soil pollution on infrastructure stability. This research aims to fill a gap by investigating how the thermal treatment process affects soil characteristics and functions. Soil samples from a railway subgrade construction site were subjected to varying temperature conditions (300, 450, and 600 °C) and treatment durations (5, 15, and 30 min) to remediate diesel-contaminated soil with a 10% TPH (Total Petroleum Hydrocarbons) concentration. The findings encompass changes in particle-size distribution (PSD), shear strength parameters (cohesion and internal friction angle), maximum dry density (MDD), and the California bearing ratio (CBR) for natural, diesel-contaminated, and thermally treated silty sand (SM). Significantly, the results underscore the effectiveness of precise control of heat exposure duration in minimizing soil degradation during oil-contaminated soil remediation. In conclusion, this study provides invaluable insights into the geotechnical properties of railway subgrade soil when treated with indirect heated microwave thermal desorption technology, offering a highly promising approach to effectively address oil-contaminated soil issues and safeguard infrastructure stability.