An array substrate, a manufacturing method thereof and a display device are disclosed. The array substrate comprises a base substrate and a thin-film transistor (TFT) unit, a color filter and a planarization protective layer disposed on the base substrate. The planarization protective layer is electrically connected with a drain electrode of the TFT unit and is conductive. The array substrate has the advantages of simplifying the layer structures of the array substrate, reducing the manufacturing difficulty of the array substrate, and improving the production yield of the array substrate.