The invention relates to a device for preventing birds from nesting on a pole tower and belongs to the technical field of electric insulation equipment. The device comprises a main board. The left andright sides of the main board are provided with buckling device. Each buckling device includes a horizontal plate and a vertical plate perpendicular to the horizontal plate. The horizontal plate is connected to the upper side of the main board by screws. The part, in contact with a cross arm, on the lower side of the main board has a rough surface. The rest part of the main board has a smooth surface. The width of the main board is 3/5 of the length of the main board. The length of the main board is equal to the sum of the two times of the height of the cross arm and [pai]/2 times of the spacing of the cross arm. The device can be stably buckled on the cross arm and prevent the birds from nesting on the cross arm.