Abstract: In order to optimize the steam distillation extraction process of essential oil from Citrus reticulata Blanco cv. Manau Gan, fresh peel samples were used as materials, and ultrasonic assisted treatment was adopted. On the basis of optimized distillation equipment and single factor tests, Box-Behnken experiment was used to design for ultrasonic temperature, ultrasonic power and ultrasonic time. The essential oils were analyzed by gas chromatography-mass spectrometry (GC-MS). The results showed that the extraction effect of Clevenger distillation apparatus was better than the other three distillation devices. The optimal oil extraction process was obtained by response surface analysis: ultrasonic temperature 33 ℃, ultrasonic power 80 W, ultrasonic time 32 min. Under the optimal conditions, the extraction yield of essential oil reached 2.50%±0.02%. Twenty-nine compounds were identified by gas chromatography-mass spectrometry (GC-MS), accounted for 99.16% of the total volatiles, including alkenes (mainly D-limonene, content up to 88.35%), alcohols (mainly Linalool 0.18%), aldehydes (mainly Octanal 0.17%), et al. This research technique could be used for the extraction of essential oil from Citrus reticulata Blanco cv. Manau Gan.