Disclosed is a broken line repair method of a TFT substrate. The method first finds out a broken line in the TFT substrate and a position of a broken point on the broken line. Then, positions of the passivation layer intersecting with the broken line at two ends of the broken point are processed, respectively to expose a metal layer, where the broken line is. Then, a metal growing film is formed on the passivation layer and the metal layer which is exposed at the two ends of the broken point. Finally, a protective film is formed on the surface of the metal growing film or the surface of the metal growing film is flattened and modified. By protecting the metal growing film or by flattening and modifying the surface of the metal growing film to reduce the roughness thereof, the breaking of the metal growing film can be prevented.