A TFT LCD array substrate and a manufacturing method thereof. The manufacturing method includes the steps of: forming a thin film transistor on a substrate to form a gate line and a gate electrode connected with the gate line on the substrate; forming a gate insulating layer and a semiconductor layer on the gate electrode; forming an ohmic contact layer on the semiconductor layer; forming a transparent pixel electrode layer and a source/drain electrode metal layer in sequence on the resultant substrate, wherein the transparent pixel electrode layer is electrically insulated from the gate line and the gate electrode, and the transparent pixel electrode layer forms an ohmic contact with two sides of the semiconductor layer via the ohmic contact layer; and performing masking and etching with a gray tone mask with respect to the resultant substrate to form a transparent pixel electrode, a source/drain electrode and a data line simultaneously.