Abstract: A kind of ultra-low volume sprayer of secondary gas-liquid two-phase flow, which is combined with knapsack electric sprayer, is developed based on the pneumatic atomization and air-assisted pesticide application. The comparative test operated in the facility greenhouse of melon against stretcher mounted sprayer showed that: the maximum application amount of ultra-low volume sprayer of secondary gas-liquid two-phase flow is 20 L/hm~2, 26.7% of the stretcher mounted sprayer. The difference of the coverage and the deposition between the positive and negative side of leaves are 3.076% and 0.268μg/cm~2, far less than stretcher mounted sprayer, which are 33.272% and 3.278μg/cm~2.Meanwhile, compared with stretcher mounted sprayer, the droplet coverage and deposition on the negative side of leaves are 9.523%,0.456μg/cm~2, more than stretcher mounted sprayer, which are 7.397%,0.406μg/cm~2. For the ultra-low volume sprayer of secondary gas-liquid two-phase flow, the uniformity of droplet coverage and deposition are more superior than stretcher mounted sprayer on the whole, especially on the negative side of leaves, the coefficient of variation of droplet coverage and deposition are 0.161 and 0.187, far less than stretcher mounted sprayer, which are 0.438 and 0.454. The test results show that: the new developed ultra-low volume sprayer of secondary gas-liquid two-phase flow is featured with excellent atomization effect, which is able to make the atomization of pesticide liquid more fully, and produce more uniform droplet. With the assistant of wind field, the droplet, with excellent penetration through canopy, is able to attached on the negative side of leaves in effect, improving the prevention effect of pesticide, achieving the purpose of application reduction and efficiency improvement of pesticide.