The present invention provides a TFT array substrate and a manufacturing method thereof. The TFT array substrate has a source electrode (801) and a drain electrode (802), which each include, stacked from bottom to top, a first molybdenum layer (811), a first aluminum layer (812), a second aluminum layer (813), and a second molybdenum layer (814). The first aluminum layer (812) and the second aluminum layer (813) each have a surface including a plurality of spikes (8120) formed and distributed thereon. The spikes (8120) of the second aluminum layer (813) have a height greater than a height of the spikes (8120) of the first aluminum layer (812) such that the source electrode (801) and the drain electrode (802) each have an upper surface exhibiting a rough surface having irregularity comprising raised and recessed portion. Compared to a flat smooth surface that is involved in the prior art, the rough surface having irregularity comprising raised and recessed portions helps expand contact area between the drain electrode (802) and the pixel electrode (1200) so as to reduce contact impedance between a TFT and the pixel electrode and improve performance of a liquid crystal display panel.