A novel method was developed for the determination of deltamethrin in air by pretreatment of membrane adsorption combined with ultrasound-assisted dispersive liquid-liquid microextraction and high performance liquid chromatography（HPLC）.The analyte was extracted with methanol-water（1∶4） solution,followed by microextraction with chloroform.After ultrasonic dispersion and centrifugation,the sedimentary facies were determined by HPLC.Deltamethrin had a good linearity in the range of 5-1000μg/L.The correlation coefficient was 0.9998 and the enrichment factor was up to 520.The average recoveries of deltamethrin from air sample at spiked levels of 10,50,100μg/L ranged from 78.6% to 106.7%,with relative standard deviations（RSDs） of 2.2%-4.3%.The limit of detection was 1μg/L,and the minimum concentration of detection was 0.04μg/m3.With the advantages of simplicity,accuracy,high extraction efficiency and low consumption of organic solvent,this method was suitable for the determination of deltamethrin in air.