At present, most domestic airassisted sprayers of orchard adjust air volume by controlling fan speed or air outlet sectional area, not realtime regulation air volume according to characteristics of fruit trees. Orchard spraying has problems of pesticide waste and insufficient spraying. In order to solve above problems, a single fan multi  duct bypassair conditioning technology was proposed. It can realize airvolume adjusted by controlling disc valve opening degree at the air outlet. In order to achieve accurate and rapid regulation of air volume, two kinds of variable air volume technologies of throttling and bypassing were designed and compared. The test results showed that the linear relationship between wind speed and butterfly valve opening of bypassing adjusting air was more obvious, which was more conducive to the control of air volume and wind speed. Bypassing air volume adjust technology was selected. Fanshaped air outlets of corresponding number were set based on number of canopy layers of fruit trees. Butterfly valve opening model based on divided canopy characteristics was analyzed and constructed, and opening of each outlet butterfly valve can be calculated according to this model. It can control butterfly valve opening combined with PID variable control technology and achieve the air volume control of each outlet for variable spray. Three spray mode among conventional air spray mode and automatic target air spray mode and variable air volume variable spray volume spray mode were selected to verify testing. The spray performance test of three operation modes was carried out based on droplet deposition and drift loss of pesticides. Test results showed that drift and ground loss of pesticides were the largest in conventional air spray mode among three spray modes. The amount of deposition on surface of canopy in variable air volume spray mode was increased by 17.3% compared with automatic target air delivery spray mode and the coefficient of variation was reduced by 10.29 percentage points. The amount of ground deposition under the canopy was decreased by 26.1%, and reduced by 40.7% between canopies. And the amount of drift was reduced by 69.9% and 50.9% compared with that of the other two spray modes. 