The invention belongs to the field of preparation of aerial spraying tools, and in particular, relates to a painting system conversion joint of a unmanned aerial vehicle. The painting system conversion joint comprises a painting tank, a conversion joint and a nozzle component, wherein a thread buckle is arranged in a tank port of the painting tank; an oil pipe is tightly passed into the painting tank through the thread buckle, and is connected to an oil inlet port of the nozzle component; an air pipe is arranged to tightly pass into the painting tank through the thread buckle, and is connected to one air outlet end of an air inlet and outlet two-way valve; the other air outlet end of the air inlet and outlet two-way valve is connected to an air inlet port of the nozzle component; an air inlet end of the air inlet and outlet two-way valve is connected to the conversion joint through a gas pipeline, and is connected with an air pump on the ground through the conversion joint; and the other way of gas connecting head is provided. The painting system conversion joint uses high-speed gas for driving spraying of gas to accelerate the speed; and as a lot of gas is mixed in liquid, the dispersibility of sprayed liquid is improved.