An organic thin film transistor and a method of manufacturing the same, an array substrate and a display device are disclosed. The thin film transistor including: a source electrode (4), a drain electrode (5), an organic semiconductor layer (6) disposed on the source electrode (4) and drain electrode (5), and a modified layer (7); the modified layer (7) is disposed at a position below an organic semiconductor layer (6) and corresponding to the source electrode (4) and the drain electrode (5), covers the source electrode (4) and the drain electrode (5), and is configured to change a contact angle on both the source electrode (4) and the drain electrode (5). The thin film transistor avoids the problems of poor formation effects and easy disconnection of the organic semiconductor layer (6) because of the large contact angle on electrode layers, and therefore reduces production costs.