The invention provides a TFT (Thin Film Transistor) substrate manufacturing method and a TFT substrate. The TFT substrate manufacturing method comprises steps of firstly etching a gate insulating layer to form two first through holes and forming two bridging metal blocks in the two first through holes, and then etching an interlayer dielectric layer to form two second through holes communicated with the two first through holes. A source and a drain are in contact with the two bridging metal blocks through the two second through holes respectively. It is possible to improve the homogeneity of the active layer and reduce the difficulty of the manufacturing process by changing the structure of the through holes of the gate insulating layer and the interlay dielectric layer formed by the traditional once etching process into the twice etching process, the problem that the etching is stopped due to the over-thick etching thickness is solved, and the product quality is improved.