A thin film transistor and a manufacturing method therefor, an array substrate, and a display panel and device. The thin film transistor includes: a gate (11) and an active layer (12) that are located on one side of a base substrate (10); a gate insulation layer (13) located between the gate (11) and the active layer (12); and a source (14) and a drain (15) that are spaced apart and both are in contact with the active layer (12), wherein a first ratio of the thickness of the gate insulation layer (13) and the thickness of the active layer (12) ranges from 3 to 4.