Many laboratory-scale studies strongly suggested that remediation of petroleum hydrocarbon contaminated soil by microwave heating is very effective; however, little definitive field data existed to support the laboratory-scale observations. This study aimed to evaluate the performance of a field-scale microwave heating system to remediate petroleum hydrocarbon contaminated soil. A constant microwave power of 2 kW was installed directly in the contaminated area that applied in the decontamination process for 3.5 h without water input. The C10–C40 hydrocarbons were destroyed, desorbed or co-evaporated with moisture from soil by microwave heating. The moisture may play an important role in the absorption of microwave and in the distribution of heat. The success of this study paved the way for the second and much larger field test in the remediation of petroleum hydrocarbon contaminated soil by microwave heating in place. Implemented in its full configuration for the first time at a real site, the microwave heating has demonstrated its robustness and cost-effectiveness in cleaning up petroleum hydrocarbon contaminated soil in place. Economically, the concept of the microwave energy supply to the soil would be a network of independent antennas which powered by an individual low power microwave generator. A microwave heating system with low power generators shows very flexible, low cost and imposes no restrictions on the number and arrangement of the antennas.