Embodiments of the present invention relates to a thin film transistor and a method for manufacturing the same, a display substrate and a display device. The thin film transistor comprises an active layer, a source electrode, a drain electrode and an ohmic contact layer, wherein the ohmic contact layer is disposed between the active layer and the source electrode and/or between the active layer and the drain electrode to improve an ohmic contact property of the active layer with the source electrode and/or the drain electrode. The present invention solves the problem of poor ohmic contact effect between the active layer and the source and drain electrodes in the existing thin film transistor, thereby improving the ohmic contact property of the active layer with the source and drain electrodes and meanwhile improving display effect of images of a display.