The present invention provides a co-planar oxide semiconductor TFT substrate structure and a manufacture method thereof. In the co-planar oxide semiconductor TFT substrate structure, the active layer comprises a main body and a plurality of short channels connected to the main body, and the plurality of short channels are separated with the plurality of strip metal electrodes to make the active layer possess higher mobility and lower leak current. Thus, the performance of the TFT element can be improved. The present invention provides a manufacture method of a co-planar oxide semiconductor TFT substrate structure. With forming the plurality of strip metal electrodes between the source and the drain, which are separately positioned, as deposing the oxide semiconductor layer, the plurality of short channels can be formed between the source and the drain. The method is simple and does not require additional mask or process to obtain the active layer structure different from prior art. The manufactured actively layer possesses higher mobility and lower leak current. Thus, the performance of the TFT element can be improved.