The invention discloses a composite thick film based on a diamond-like carbon thin film and a coating method of the composite thick film. The composite thick film comprises a metal base layer, a transition layer and a diamond-like carbon layer which are successively formed from the surface of a substrate to the outside, wherein the transition layer is a mixture layer which is formed by stacking two film layers in a staggered manner by simultaneously using a magnetron sputtering technology and an enhanced type cathode arc technology; and the thickness of the diamond-like carbon layer is between 1 mu m and 10 mu m. The composite thick film is exquisite in design and simple in structure; the transition layer has the structure which is formed by stacking the two film layers in the staggered manner, the advantages of small internal stress of a magnetron sputtering film layer and large hardness of an enhanced type cathode arc film layer are played fully, large hardness and small internal stress of the transition layer are combined effectively, large hardness and small stress facilitate increasing of the thickness of the diamond-like carbon layer, and the thickness of the finally formed composite thick film reaches 20 mu m or above; and moreover, huge stress caused by a thick film function layer can be buffered effectively, therefore, the binding force of the composite thick film and the substrate is guaranteed, and meanwhile, surface defects of the composite thick film can be reduced effectively.