The invention relates to a method for preparing a carbon nano tube enhanced metal matrix composite material through welding, and belongs to the field of metal matrix composite materials. Carbon nao tubes are taken and placed in mixed acid to be purified, the purified carbon nano tubes are added in absolute ethyl alcohol to be subjected to ultrasonic scattering, carbon nano tube suspension liquid is obtained, a modification agent and a surface active agent are sequentially added in the suspension liquid, the carbon nano tubes are placed in a refrigerator to be subjected to standing, and modified carbon nano tubes are obtained through centrifugal separation; a copper plate is taken as a base material, laser treatment is conducted after polishing, a copper plate base material subjected to laser treatment is obtained, the modified carbon nano tubes are welded to the copper plate base material, and then the carbon nano tube enhanced metal matrix composite material can be obtained. Modification and treatment are conducted on the carbon nano tubes and the base material correspondingly, and the carbon nano tubes are evenly scattered on the surface of the base material. Due to usage of the welding technology, the carbon nano tubes can be well embedded in the copper plate base body material and can be well combined with the base body interface, and the mechanical performance of the composite material can be improved.