Atree cutting-down tool for cutting down trees under leads comprises a hook, a hinge pin, an insulating control rod and an insulating rope, wherein a small hole is formed in a position, which is close to the tail, of the hook, and the hook is hinged to the insulating control rod through the hinge pin; a through hole for tying the insulating rope is formed in the tail of the hook, and one end of the insulating rope is tied on the through hole. The tool has the advantages as follows: the tool is simple in principle structure and good in practicability and has a control function; a worker can use the tool on a near-electricity side through the insulating tree cutting-down hook, and the application range is wide; during cutting down of trees, the worker controls the special tree cutting-down hook on the ground to fix the trees to control falling directions of the trees, so that falling of persons due to the fact that corresponding persons climb the trees to tie ropes is avoided. When the trees are fixed by the tree cutting-down hook, the working state can be adjusted under the control action of the insulating rope, the working efficiency is improved, and the lead power outage handling time is shortened greatly; and the tool is simple to operate, firm, durable and good in stability.