Abstract: The optimization of the essential oil extracted from pepper leaves by deep eutectic solvents was carried out using one-factor-at-a-time method and response surface methodology. Using a Box-Behnken design,a mathematical model was established to investigate the effects of solvent-solid ratio,ultrasonic power and extraction time on the yield of essential oil,respectively. The results showed that the most suitable deep eutectic solvent was choline chloride/urea. The optimum conditions of pepper leaves essential oil were as follows:The solvent-solid ratio was 14:1 mL/g,the ultrasonic power was 300 W,the extraction time was 53 min. Under the optimal conditions,the yield of essential oil of pepper leaves was 1.380%±0.018%,which was better than steam distillation and ultrasonic-assisted steam distillation. The yield of pepper essential oil increased by 14.33% and 5.18%,respectively. A total of 34 compounds were identified by GC-MS. The main components of essential oil were δ-elemene(19.75%),α-cubebene(9.17%),caryophyllene(8.97%),α-gurjunene(6.12%),β-eiemene(5.13%).The method for extracting pepper leaves essential oil by using choline chloride-urea as deep eutectic solvent is feasible.