In order to prepare hydrocarbon fuel, sodium soap made from Swida wilsoniana fruit oil was chosen as a model compound with significant molecular polarity for preparing hydrocarbon fuel by microwaveassisted pyrolysis. The result showed that the hydrocarbon content were usually above 70%. In addition, its density and dynamic viscosity were 0.850～0.875 /cm3 and 2.09～2.85 mm2/s, respectively, similar with petroleum diesel. The highest peak in the GC-S profile of liquid product was fifteen carbon alkenes, decarboxylation was proved to be main reaction in microwaveassisted pyrolysis.