The invention discloses a four-rotor plant protection unmanned aerial vehicle adopting a helicopter armor plate structure. The four-rotor plant protection unmanned aerial vehicle is mainly composed of a fuselage, a dynamical system, an avionics system and a spraying pod. The four-rotor plant protection unmanned aerial vehicle fully absorbs the advantages of simple structure and easiness in control of a multi-rotor structure, and the advantages of high aerodynamic efficiency, high space utilization and the like of a helicopter. Guard boards, partitions and pull rods are constructed to form a main frame, support arms are fixedly connected to the guard boards, all the devices are arranged on the partitions between the guard boards and in the space defined by the partitions and the pull rods, the space utilization rate is very high, and simplicity, practicality and attractiveness are realized, so that the phenomena of bondage and independent suspension of the traditional horizontal layout structure are avoided. In addition, the helicopter armor plate structure is in the vertical layout, the stress state is more reasonable, the aerodynamic layout efficiency is obviously improved, and the power consumption is significantly reduced.