The invention discloses a novel bird nesting preventing device for a power facility. The device comprises a bird repelling assembly which is fixedly connected with the power facility through a lockingassembly, the bird repelling assembly comprises telescopic balls with telescopic degree of freedom which are formed by a group of moving assemblies which are hinged to each other, upper connecting plates on the moving assemblies are hinged to a group of first connecting rods, lower connecting plates are hinged to a group of second connecting rods, the first connecting rods and the second connecting rods are crossedly arranged, the intersection points are hinge nodes, the first connecting rods in the adjacent moving assemblies are hinged to each other, the second connecting rods in the adjacent moving assemblies are hinged to each other, a second hinged shaft of the two second connecting rods which are hinged to each other horizontally crosses above a first hinge shaft of the two first connecting rods which are hinged to each other, the distances between the adjacent telescopic balls in a stretching state and pull rope fixing points on the telescopic balls in a retracting state are equal to a pull rope, the stretching and retracting of one another of the telescopic balls can be achieved through the pull rope and the gravitational force of birds, and a bird repelling effect can be achieved without wind.