The invention discloses a shade tree protective paint spraying device. The device comprises a main box body, wherein the main box body is internally provided with an up-down sliding cavity with a leftward opening, a front gear is internally in sliding fit connection to a working sliding block, an up-down through sliding rod cavity is arranged in the working sliding block, the left side of the sliding rod cavity is in communication with a pushing rod cavity with a leftward opening, the upper portion of the up-down sliding cavity is in communication with a semi-open cavity, a conical tooth cavity is provided in the upper portion of the semi-open cavity, the left side of the conical tooth cavity is provided with a belt pulley cavity, an openable and closable annular device may be used for surrounding trunks of different thicknesses, internal nozzles continuously perform annular motion during lowering of the annular device, so that the nozzles finally realize spiral motion relative to thetrunks during a working process, spraying on the trunks is more uniform under such motion, and compared with a traditional mode, a spraying liquid can be saved while time is saved.