An array substrate includes a base substrate (10) and a gate line (11) and a data line (12) provided on the base, the gate line (11) and the data line (12) define a pixel unit, and in the pixel unit, a thin film transistor (13) is provided, the thin film transistor (13) includes a gate electrode (131), a gate insulation layer (132), an active layer (133), a source electrode (134) and a drain electrode (135). The gate insulation layer (132) includes a first gate insulation portion (1321) and a second gate insulation portion (1322), the gate electrode (131) is located between the first gate insulation portion (1321) and the second gate insulation portion (1322), and the second gate insulation portion (1322) is located between the gate electrode (131) and the active layer (133). The array substrate further includes a conductive pad (114), and a first via (15) corresponding to the conductive pad (114) is provided in the gate insulation layer (132) at both sides of the gate line (11), and the data line (12) is connected to the conductive pad (114) through the first via (15). The array substrate is capable of improving the definition, the resolution and the aperture ratio of a display device. A manufacturing method for an array substrate and a display device including such an array substrate are also disclosed.