An array substrate and a manufacturing method thereof are provided. The manufacturing method includes steps of: providing a first substrate; providing a first mask and arranging active switches on the first substrate; providing a second mask, forming a photoresist layer on the active switches and sequentially performing following steps of: performing a first wet etching on the active switches, performing a first ashing treatment on the photoresist layer, performing a first dry etching on the active switches, performing a second wet etching on the active switches, performing a second ashing treatment on the photoresist layer and performing a second dry etching on the active switches; providing a third mask and forming a protective layer on a metal layer of the active switches; and providing a fourth mask and forming a pixel electrode layer on the protective layer.