A method for manufacturing a dual gate oxide semiconductor TFT substrate utilizes a halftone mask to implement a photo process, which not only accomplishes patterning to an oxide semiconductor layer but also obtains an oxide conductor layer with ion doping. The method implements patterning to a bottom gate isolation layer and a top gate isolation layer at the same time with one photolithographic process. The method implements patterning to second and third metal layers at the same time to obtain a first source, a first drain, a second source, a second drain, a first top gate and a second top gate with one photolithographic process. The method implements patterning to a second flat layer, a passivation layer and a top gate isolation layer at the same time with one photolithographic process. The number of photolithographic processes involved is reduced to nine so as to simplify the manufacturing process.