Air-assisted spraying technique research was carried out to increase pesticide efficiency and decrease pesticide loss. The spraying performance was experimentally studied on model 3WQ-3000 trailed air-assisted boom sprayer in small bell stage of corn fields. The effects of four sizes of flat fan nozzles（ST110-02, ST110-04, ST110-05, ST110-06） with air curtain on pesticide efficacy, coverage rate and loss rate were carried out. The experiment results showed that the deposition amount was large at upper part of corn canopy and small at lower part. Air curtain enhanced penetrability, deposited property of droplets and improved the uniformity of distribution at corn canopies. Air-assisted sprayer had significant influence on small size droplets VMD that the pesticide efficacy of ST110-02 flat fan nozzle with air curtain was 83% more than that without air curtain. The optimum pesticide efficacy of ST110-06 flat fan nozzle with air curtain was 41.93%. Air curtain could increase pesticide loss rate on the ground. The best loss rate of ST110-02 flat fan nozzle without air curtain was 13.05%. Compared with the conventional sprayer, the new airassisted sprayer had better droplet coverage rate and higher penetrability, the average pesticide efficacy was improved by 144.17%, and pesticide loss rate on the ground was reduced by 14.46%.