The invention relates to a propeller with variable pitch. According to the propeller, a spiral spring is arranged in the middle of the upper surface of a base, blade shanks of two blades are respectively placed in blade shank chutes on two sides of the spiral spring, synchronization rods are hinged to the end surfaces of the two blade shanks, the other ends of the synchronization rods are connected with synchronization plates in a reducing synchronization mechanism, connecting sheaths of a reducing restraining mechanism sleeve the ends, hinged with the synchronization rods, of the blades, and the sliding rails are arranged in blade shank chutes in the base. The positions of the synchronization plates on the surface of the base correspond to those of spiral springs on the synchronization plates, and the synchronization plates sleeve inner connecting shafts of the spiral springs. Linear bearings sleeve one ends of two blade shanks. The propeller is in four states during use, the pitch of the propeller is controlled according to the centrifugal force of the blades during rotation. And the propeller has the characteristics of simple structure and low energy consumption.