The invention relates to the technical field of semiconductor integrated circuits, in particular to a high-entropy alloy diffusion barrier layer for a Cu interconnect integrated circuit and a preparation method of the high-entropy alloy diffusion barrier layer for the Cu interconnect integrated circuit. The high-entropy alloy diffusion barrier layer for the Cu interconnect integrated circuit sequentially comprises a Si substrate layer, a high-entropy alloy intermediate coating and a Cu film from bottom to top, wherein the high-entropy alloy intermediate coating sequentially comprises a third coating, a second coating and a first coating from bottom to top; the first coating is an AlCrTaTiZrMo high-entropy alloy coating; the second coating is a pure Ti coating; and the third coating is an AlCrTaTiZrMoNx high-entropy alloy coating. According to the high-entropy alloy diffusion barrier layer for the Cu interconnect integrated circuit, improvement of the atomic bulk density is facilitated,generation of defects, such as vacancies is reduced, a diffusion channel for atoms is reduced, and the diffusion barrier performance and the heat stability of the high-entropy alloy coatings are improved.