The invention relates to a helicopter propeller position changing device, and belongs to the field of engineering machinery. According to the helicopter propeller position changing device, before position changing, the short sides of stoppers penetrate through holes V in the side faces of a box body, and the long sides of the stoppers penetrate through holes of the two ends of position changers II; when position changing is needed, an electromagnet is electrified, the short sides of the stoppers are separated from the holes V in the side faces of the box body, the long sides of the stoppers penetrate through holes of the two ends of position changers I, at the moment, a bevel gear I rotatably drives bevel gears II to rotate together, the bevel gears II drive the position changers I to rotate together, as the long sides of the stoppers are located in the position changers I at the moment, the position changers I drive the stoppers to rotate together, the stoppers drive the position changers II to rotate, and the position changers II drive propeller vanes to rotate to achieve the position changing; and after the position changing is completed, the electromagnet is subjected to power failure, and, at the moment, the stoppers are pushed to the direction of the box body by springs, so that the stoppers get back to the positions of new holes V in the box body. According to the helicopter propeller position changing device, the propeller vanes can rotate freely relative to an axle center free of influence of wind thrust.