Abstract: In order to mechanize the pesticide application of fence-type fruit tree, enhance the droplet deposition in canopy and improve work efficiency, a combined disc air-assisted orchard sprayer was developed. The mechanism design theory and virtual prototyping technology were adopted to design the disc atomizer and combined spray execution device. Single impeller was put to use in disc atomizer design, and the diameter of impeller was 0.4 m. Six-step motors were included in the combined spray execution device for lifting, rotating and contraction, the rotating and lifting speed were 4 rad/s and 0.12 m/s, respectively. The adjustable range of spray height was from 3 to 4 m, and the hemi-spray width was adjustable from 2 to 3 m. So it was suitable for the fence-type orchard with row spacing of from 4 to 6 m. The container's capacity was 1 000 L, and the spray volume was 51.63 L under the rated working pressure of 0.4 MPa. The distance of the run was up to 1 500 m, and the work efficiency was 2 times of single spray. The average spray volumes of the 8 nozzles of disc atomizer were 807, 894 and 1 020 mL/min under the pressures of 0.4, 0.6 and 0.8 MPa respectively, while the standard deviations were 7.4, 8.2 and 7.8. It showed that spray volumes of different nozzles had small change, while spray volume increased with the increasing of spray pressure. The droplet diameters at 0.5, 1, 1.5, 2, 3, 4, 5, 6, 7 and 8 m along the direction of range were measured by DP-02 laser particle size analyzer under the pressures of 0.4, 0.6 and 0.8 MPa. The droplet diameters were 140, 135 and 122 μm in the distance of 2 m from the nozzle. The maximum diameter was in the distance of 4 m from the nozzle. The diameter decreased as the distance increased when the distance was greater than 4 m, while the diameter increased as the distance increased when the distance was less than 4 m. Spray deposition in vertical direction was mainly between 1 and 2 m above floor, and the maximum deposition was between 1.4 and 1.6 m. The data offered the basis to confirm the spray distance and guide the installation of disc atomizer. The fan property was tested and the performance curve graphic was drawn. Frequency transformer, torque meter and wind velocity indicator were used. The results showed that air volume was greater than 1 m3/s, and static pressure was greater than 60 Pa when the speed was greater than 1 300 r/min. The highest efficiency was 89% at 1 400 r/min. Execution time of each executive unit per stroke was 51.3 s for up and down, 50.5 s for stretch and draw and 26.5 s for rotation. The field experiment was conducted in Taizhou, which strictly followed the quality standard of air-assisted orchard sprayer (GB/T 24683-2009). The row space was 4 m × 2 m, the crown diameter of the tree was 0.7 m, and the height of the tree was 1.9 m. Three trees were randomly selected as sample trees. The intersection points of 3 horizontal layers and 3 vertical layers of each tree were set as sample points, with a total of 9 sample points for one tree. The result showed the pesticide was evenly distributed in the exterior of canopy, and the average coverage of the left and right were 55.13% and 52.60% respectively for the front of the leaf, and 6.57% and 7.14% respectively for the back of the leaf. The interior deposition was less than the exterior, but the spraying coverage was relatively even in the front and rear of the leaf, 12.77% and 9.74%, respectively. This study proposes a new machine of plant protection for the fence-type fruit tree, and also provides the reference for optimum design of orchard air-assisted sprayer.