The invention relates to the technical field of plant protection machinery, and provides a biomass sphere putting system and method for an unmanned aerial vehicle. The putting system involves a control module, a sphere storage device, a stirring device, a sphere feeding device and a releasing device; the stirring device is located in the sphere storage device and is connected with the sphere storage device; the sphere feeding device is connected with the stirring device and the releasing device; the control module is electrically connected with the stirring device and the releasing device; andin the putting process, the stirring device is used for continuously stirring biomass spheres so that the biomass spheres can smoothly enter the sphere feeding device, the sphere feeding device is used for separating and conveying the biomass spheres, the biomass spheres can be controlled to be released by the releasing device, and the biomass spheres are thrown out one by one according to the operation requirement. According to the system and method, the blockage and overhead phenomenon of the biomass spheres can be removed, the spheres are arranged at a releasing port according to a certainposition height, so that the continuity of sphere throwing is ensured; and biomass sphere releasing can be autonomously controlled, timing and quantitative releasing is realized, the reliability andthe stability of releasing are improved, and the automation degree is high.