An array substrate and a manufacturing method thereof, a liquid crystal display panel and a display device are provided, the array substrate comprises a base substrate, and thin film transistors and pixel electrodes provided on the base substrate, the pixel electrode and the active layer in the thin film transistor are provided in the same layer. The active layer is formed of transparent oxide semiconductor material, and the concentration of carriers in the oxide semiconductor material may be increased by performing a plasma process on the oxide semiconductor material, thus the pixel electrode may be manufactured by using the oxide semiconductor material used for manufacturing the active layer, thereby the pixel electrode and the active layer can be provided in the same layer, the number of the masks can be reduced, the manufacturing process is simplified, production cost is saved, the productivity is increased, and the manufacturing time is shortened.