An unmanned multi-rotor spray aircraft was designed to solve the problems existed in southern China including the complex operational environment of agriculture,scattered distribution of farmland,low efficiency of manual spraying operations.This aircraft has advantages of high efficiency,low labor intensity,good adaptability to operating environment.The vehicle frame adopts full carbon fiber structure,hardened aluminum connecting parts. The structure is stable and reliable.It can keep working 15 minutes under the condition of continuous operation with the load of 10 kg.It will provide a reference for spray,forestry,forest monitoring.