Embodiments of the invention provide a conductive structure, a thin film transistor, an array substrate, and a display device. The conductive structure comprises a copper layer formed of copper or copper alloy; a blocking layer for preventing copper ions of the copper layer from diffusing outward; and a diffusion prevention layer for preventing exterior ions from diffusing to the copper layer and disposed between the copper layer and the blocking layer. The multilayer conductive structure according to an embodiment of the invention can prevent exterior ions from diffusing into a copper layer and prevent copper ions from diffusing outward to reduce ions diffusion that adversely impacts the electricity performance and chemical corrosion resistance of the copper metal layer, and meanwhile can enhance adhesiveness of the conductive structure, which may be helpful for etching/patterning of the multilayer conductive structure.