There is an urgent need for new chemical application techniques and sprayers in Chinese orchard spraying, because of the requirements of environment pollution, safety for food and operator during chemical application in Chinese orchards.One type of new automatic target detecting based on size of canopy with variable chemical dosage and air-flow of fan orchard sprayer was designed and developed to meet the demand of chemical pest control in orchards.The techniques of automatic target detection, multi-sensors, electrostatics, and air-assisted spraying were combined within this system.Two kinds sensors, Infrared ray sensor and laser light sensor were incorporated for this sprayer to detect with or no-target for spraying and to get the dates of orchard canopy size for chemical application on-line, the control units can calculate how much liquids of chemical need to be sprayed according to the size of tree canopy at the same time.The sprayer can automatically open and stop the nozzle for spraying chemical liquids, when the infrared sensor find target of tree, the nozzle will be opened, when the infrared sensor find the interstitial space between the trees, the sprayer will automatic stop to spray, meanwhile the chemicals liquids and air volume of fan will be variable adjusted for the spraying in the light of size of tree canopy by the control units in this developed system.This sprayer light weighted,highly efficient, reduces pesticide use and is friendly to the environment.The electrostatically charged droplets are projected toward the target by the assist of an air stream that increases the droplets penetration with in canopy.Experimental results show that the new automatic target detecting orchard sprayer with an infrared and laser sensor can save more than 50 to 80% of pesticides, improve the utilization rate (55-75%), control efficiency, and significantly reduce environmental pollution caused by the application.At the same time the key technological problems related to amounted chemical liquid, air volume and electrostatic spraying are solved.