The detection and treatment of polycyclic aromatic hydrocarbons in farmland are related to the environmental quality of farmland soil and the food security of residents. A method is described for determination of pyrene, a representative pollutant of polycyclic aromatic hydrocarbons in farmland, by high performance liquid chromatography with ultrasonic extraction. The results showed that the optimal extraction method for the determination of pyrene in farmland soil was 2.00 g soil sample, with dichloromethane-n-hexane (1:1, V:V) mixed solvent as the extractant, and 10 mL of extraction solvent was extracted (50 kHz, 40 min) sonically twice and concentrated by nitrogen blowing at 40 °C. The results showed that the linear relationship of the pyrene standard curve was good, the correlation coefficient was 0.9997, and the detection limit was 0.54 μg/kg. In the range of pyrene concentration of 0.1-50 mg/kg, the average recovery rate of spiked soil was 72.55%-89.66%, and the relative standard deviation was 1.68%-4.27%. This method has the advantages of simple operation, less time-consuming and less solvent consumption, and has practical significance for improving the detection efficiency of pyrene contaminated soil samples and carrying out research on the remediation and treatment of pyrene pollution in farmland.