The present disclosure discloses a manufacturing method of a polycrystalline silicon thin film, which includes: forming a first amorphous silicon thin film; crystallizing the first amorphous silicon thin film to form a polycrystalline silicon thin film by applying an excimer laser annealing process; forming a second amorphous silicon thin film on a first surface of the polycrystalline silicon thin film; and etching until the second amorphous silicon thin film is completely removed toward a direction of the polycrystalline silicon thin film from the second amorphous silicon thin film by applying a dry etching process. The present disclosure further discloses a manufacturing method of a thin film transistor array substrate which includes the steps of manufacturing an active layer: forming a layer of a polycrystalline silicon thin film according to the previous polycrystalline silicon thin film; and etching the polycrystalline silicon thin film to form a patterned active layer.