The experiment levels of Lagerstroemia indica fruit volatile oil（LIFVO）were first evaluated using single-factor method, after which the selected levels were used to optimize ultrasonic extraction process with the response surface Box-Behnken design. The optimal extration conditions of LIFVO were found to be 47 min, 562 W, 69 ℃, liquid-solid ratio 23.6:1 mL/ g. Based on the suggested process, the obtained response value was 2.72?0.02 %. GC-MS was used to characterise the compounds of LIFVO. Twenty-eight compounds were identified. The major components of LIFVO were tetradecane (17.307 %), pentadecane (12.731 %) and hexadecane (10.897 %). Results of bacteriostatic research suggested that the LIFVO can significantly inhibit the growth of tested bacteria. And the main antibacterial components in LIFVO are a variety of straight chain alkanes and?Α-Bilberry solanesol.?