Lightweight high clearance boom sprayer with airassisted system was designed to develop efficient pesticide application technologies for soybean at middle and later growing stages. The sprayer wheel tread can be adjusted from 1600mm to 1750mm, ground clearance was 800mm, wheel base was 2000mm, spray span was 8000mm. Various soybean field experiments were conducted to measure the performance of airassisted spraying system on lightweight high clearance boom sprayer. The experiment results showed that when the operating speed was 4km/h, droplet coverage rate of the positive soybean leaves surface was increased by 19.0 percentage points in upper canopy and 17.0 percentage points in middle canopy, while that in lower canopy was increased by less than 5.0 percentage points through improving the spray pressure. Droplet coverage rate of back soybean leaves surface was increased by 5.5 percentage points in upper canopy and 2.3 percentage points in middle canopy, and that in lower canopy was increased by less than 1.0 percentage points. Droplet coverage rate by using ST110-05 nozzle was improved by 21.0 percentage points, 26.0 percentage points and 10.0 percentage points compared with that by using ST110-03 nozzle on the positive soybean leaves surface in upper, middle and lower canopies, respectively. Droplet coverage rate by using ST110-05 nozzle was increased by 5.0 percentage points and 1.0 percentage points in comparison with that by using ST110-03 nozzle on the back soybean leaves surface in upper and middle canopies, respectively, and no significant influence on lower canopy. When the air speed of curtain was 11.5m/s, the airassisted system could make the droplet coverage rate of positive soybean leaves surface increase by 26.8 percentage points and 22.0 percentage points in middle and lower canopies, respectively. The droplet coverage rate of back soybean leaves surface was increased by 23.1 percentage points, 18.1 percentage points and 8.4 percentage points in upper, middle and lower canopies, respectively. The assisted air flow had strong penetrability which was shown in the droplet coverage rate on positive and back leaves surfaces, and improved the distribution uniformity in soybean canopies. However, the droplet loss rate on the ground was increased.