The present invention teaches a TFT array substrate and its manufacturing method including the following steps. A data line and a ring-shaped source electrode are formed on a substrate. A first insulation layer is formed on the substrate. A ring trough exposing the source electrode is formed on the first insulation layer. A semiconductor active layer is formed in the ring trough. A channel is formed on the first insulation layer in an area surrounded by the ring trough. A gate line, a gate electrode in the channel, and a drain electrode connected to the semiconductor active layer are formed on the first insulation layer. A second insulation layer is formed on the first insulation layer, and a pixel via is formed on the second insulation layer. A pixel electrode is formed on the second insulation layer, and is connected to the drain electrode through the pixel via.