The invention discloses an active early-warning type anti-climbing device for a power transmission line. The early-warning type anti-climbing device comprises an anti-climbing alarm expelling device and an anti-climbing structure; the anti-climbing structure comprises a cylinder wrapping a telegraph pole, the bottom of the cylinder and the ground are fixedly mounted, and the height of the cylinderis greater than the maximum height that arms can touch in a lifting state when people stands; and the anti-climbing alarm expelling device comprises a controlling box arranged in the cylinder, the controlling box is internally provided with a power supply box, a controller and an alarm device, the controller comprises a control circuit and a sensing device, and the alarm device and the sensing device are electrically connected with the control circuit. The active early-warning type anti-climbing device for the power transmission line is simple in structure, comprises various anti-climbing modes, and can be applied to urban or villages and even rural mountain forest, and the problems that in the prior art, an anti-climbing structure of a telegraph pole is simple, low in protecting performance, prone to being damaged and the like are solved.