The invention provides a thin film transistor, a preparation method thereof and a display device. The thin film transistor comprises a gate electrode and an active layer which are arranged on a substrate, wherein the gate electrode is in an arch shape, and the active layer is arranged in the arch in a penetrating mode, and a channel surrounded by the gate electrode is formed. By forming the channel annularly surrounded by the gate electrode, the area of the thin film transistor is effectively reduced, the high-resolution requirement is met, and the problem that the resolution of an existing structure is difficult to improve by reducing the area of the thin film transistor is effectively solved. And meanwhile, through the structure that the gate electrode annularly surrounds the channel, the control of the gate electrode on the channel conductivity is enhanced, and the driving capability and the working stability of the thin film transistor are effectively improved.