The invention relates to a laser device, and particularly relates to a carbon dioxide laser with an oil liquid cooling sleeve. The carbon dioxide laser comprises a laser, wherein the two ends of the laser are respectively provided with an output lens and a reflection lens; the output lens is provided with the output lens cooling sleeve, and a sleeve shell with a sealing end and an opening end is sleeved on the end part, in which the laser is arranged, of the reflection lens; an insulating mat is arranged between the opening end of the sleeve shell and the laser and is used for sealing a gap between the sleeve shell and the laser, and the end part in which the reflection lens is arranged, of the laser and the reflection lens are sealed in a sealing cavity arranged between the sleeve shell and the insulating mat; and a cooling liquid is filled in the sealing cavity arranged between the sleeve shell and the insulating mat, and the end part of the outer side of the shell is provided with a cooling device. The cooling liquid can transfer heat of the reflection lens and the end parts of the laser onto the sleeve shell, the heat is cooled through the cooling device, and the cooling reflection lens and the laser are arranged on the end parts of the reflection lens.