A manufacturing method of a thin film transistor, the thin film transistor comprising a gate electrode, a gate insulation layer, an active layer, an ohmic contact layer, a source electrode and a drain electrode, wherein the method comprises: forming the ohmic contact layer by an injection process; forming a groove divided into a first region and a second region in the gate insulation layer; forming the active layer in the first region; and forming the ohmic contact layer in the second region by the injection process; characterized in that: a conductivity of the ohmic contact layer is not uniform, and the method comprises: forming a photoresist layer on the gate insulation layer; performing exposing and developing processes on the photoresist layer by using a multi-tone mask plate so as to form a photoresist-completely-removed region, a first to n-th photoresist-partially-retained regions (533, 534) and a photoresist-completely-retained region, wherein n is an integer greater than 2, thicknesses of the photoresist in the first to n-th photoresist-partially-retained regions (533, 534) are gradually increased, and the photoresist-completely-removed region 531) corresponds to a region where the active layer is to be formed, the first to n-th photoresist-partially-retained regions (533, 534) correspond to a region where the ohmic contact layer is to be formed, and the photoresist-completely-retained region corresponds to other region; etching the gate insulation layer in the photoresist-completely-removed region to form the first region, and then forming the active layer in the first region; removing the photoresist in the first photoresist-partially-retained region and etching the gate insulation layer in this region to form a first portion of the second region, and then forming a first sub-ohmic-contact-layer (505a-1) in the first portion of the second region by using the injection process; removing the photoresist in the second photoresist-partially-retained region and etching the gate insulation layer in this region to form a second portion of the second region, and then forming a second sub-ohmic-contact-layer (505a-2) in the second portion of the second region by using the injection process; in the same way as that for forming the first sub-ohmic-contact-layer (505a-1) and the second sub-ohmic-contact-layer (505a-2), forming a third sub-ohmic-contact-layer (505a-3) up to a (n-1)-th sub-ohmic-contact-layer; removing the photoresist in the n-th photoresist-partially-retained region (532, 533, 534), and etching the gate insulation layer (303; 403; 503) in this region to form a n-th portion of the second region, and then forming a n-th sub-ohmic-contact-layer in the n-th portion of the second region by using the injection process; and removing the photoresist in the photoresist-completely-retained region. forming a photoresist layer on the gate insulation layer; performing exposing and developing processes on the photoresist layer by using a multi-tone mask plate so as to form a photoresist-completely-removed region, a first to n-th photoresist-partially-retained regions (533, 534) and a photoresist-completely-retained region, wherein n is an integer greater than 2, thicknesses of the photoresist in the first to n-th photoresist-partially-retained regions (533, 534) are gradually increased, and the photoresist-completely-removed region 531) corresponds to a region where the active layer is to be formed, the first to n-th photoresist-partially-retained regions (533, 534) correspond to a region where the ohmic contact layer is to be formed, and the photoresist-completely-retained region corresponds to other region; etching the gate insulation layer in the photoresist-completely-removed region to form the first region, and then forming the active layer in the first region; removing the photoresist in the first photoresist-partially-retained region and etching the gate insulation layer in this region to form a first portion of the second region, and then forming a first sub-ohmic-contact-layer (505a-1) in the first portion of the second region by using the injection process; removing the photoresist in the second photoresist-partially-retained region and etching the gate insulation layer in this region to form a second portion of the second region, and then forming a second sub-ohmic-contact-layer (505a-2) in the second portion of the second region by using the injection process; in the same way as that for forming the first sub-ohmic-contact-layer (505a-1) and the second sub-ohmic-contact-layer (505a-2), forming a third sub-ohmic-contact-layer (505a-3) up to a (n-1)-th sub-ohmic-contact-layer; removing the photoresist in the n-th photoresist-partially-retained region (532, 533, 534), and etching the gate insulation layer (303; 403; 503) in this region to form a n-th portion of the second region, and then forming a n-th sub-ohmic-contact-layer in the n-th portion of the second region by using the injection process; and removing the photoresist in the photoresist-completely-retained region.