A manufacturing method of a thin film transistor array panel includes forming a gate line on a substrate and a gate insulating layer on the gate line, forming a semiconductor on the gate insulating layer, forming a first data line and a first drain electrode on the semiconductor, forming a lower passivation layer on the first data line and the first drain electrode, forming an upper passivation layer on the lower passivation layer and a metal layer on the upper passivation layer, etching the metal layer by using a photosensitive film as a mask to form a reflecting electrode and to expose the lower passivation layer, etching the exposed lower passivation layer to form a first contact hole exposing the first drain electrode, and forming a connection assistance member connecting the first drain electrode and the reflecting electrode through the first contact hole after removing the photosensitive film.