Disclosed is a thin film transistor, including a gate electrode, a source electrode and a drain electrode. The source electrode includes a loop structure with an opening, and a width of the opening is less than a maximum width of an inner ring of the loop structure of the source electrode in a direction identical to a direction of the width of the opening. The drain electrode is surrounded by the loop structure, and is not in contact with the source electrode. The drain electrode is distant from the inner ring of the loop structure of the source electrode at a same interval.