The invention discloses an array substrate, a manufacturing method thereof, a display panel and a display device, and belongs to the technical field of display. The array substrate comprises a substrate body, and a grid electrode metal pattern and grid lines are formed on the substrate body; a grid electrode insulating layer is formed on the substrate body where the grid lines are formed; a data line and a source drain electrode metal pattern are formed on the substrate body where the grid electrode insulating layer is formed; a passivation layer is formed on the substrate body where the source drain electrode metal pattern is formed; a first via hole set is formed in the grid electrode insulating layer and located above the grid lines, a second via hole set, a third via hole set and a fourth via hole set are formed in the passivation layer, the second via hole set is located above a drain electrode, the third via hole set is located above the grid lines, the third via hole set is communicated with the first via hole set, and the fourth via hole set is located above the data line; and a pixel electrode pattern, a first testing electrode pattern and a second testing electrode pattern are formed on the substrate body where the passivation layer is formed. The problem that a product is low in yield is solved, the product yield is increased, and the array substrate is used for the display device.