The invention provides a manufacturing method of TFT substrate and a TFT substrate. The method provides a dual-gate structure symmetrically disposed on both sides of active layer, which prevents TFT threshold voltage from changing and improve TFT conduction state switching; by first manufacturing the active layer before the gate insulating layer to make the insulating layer directly grow on active layer, the contact interface between the gate insulating layer and active layer is improved, leading to further improving TFT conduction state switching. The TFT substrate makes the gate located between the source and the pixel electrode in vertical direction, and the dual-gate is symmetrically disposed on both sides of active layer to prevent TFT threshold voltage from changing and improve TFT conduction state switching, as well as improve the contact interface between the gate insulating layer and active layer, leading to further improving TFT conduction state switching.