An FFS mode LCD and a fabrication method thereof are provided. The fabrication method comprises: etching a common electrode material and a gate metal on a board at the same time through a first mask process; forming a gate insulating layer, an active layer and a source/drain metal on the board; forming a channel in a TFT part, forming an opening in the pixel area part by diffraction exposure and exposing a gate pad part through a second mask process; forming a passivation layer substantially on board, and forming a contact hole in TFT part, etching regions in pixel area part and exposing a gate pad and a data pad part through a third mask process; and forming a pixel electrode on regions of the TFT, pixel area part and opened regions of the gate pad and data pad part through a fourth mask process.