Abstract: In this study,the Lactuca sativa L. homogenate was used as the test material to establish the pre-treatment process of polycyclic aromatic hydrocarbons in vegetables. Six experimental conditions including sample quality,extract volume,ultrasonic extraction time,sulfuric acid volume,sulfuric acid concentration andeluent type were determined by was single factor experiment. Then the pre-treatment process was optimized by orthogonal test.The results showed that the optimum pretreatment conditions were 52 mL of extract volume,14 g of sample mass,ultrasonic extraction for 38 min,13 mL of sulfuric acid volume,35% of sulfuric acid,eluent type of 6 mL n-hexane and 6 mL dichloromethane/n-hexane(V₁:V₂=3:7). Under these conditions,the content of plycyclic aromatic hydrocarbons was up to 961.541 μg/kg. The recovery rate of the process was 80.54%~142.04%,and the RSDs were 1.35%~8.96%,indicating the method had good accuracy and precision. The pretreatment process established by the orthogonal method had many advantages,mainly including simple sample preparation,powerful ability to detect a large number of samples at the same time,and a good repeatability,could be applied to the extraction of polycyclic aromatic hydrocarbons in vegetables.