The invention discloses an array substrate and a preparation method thereof. The array substrate comprises a substrate, a buffer layer, a
semiconductor pattern layer, a first grid
electrode insulation layer, a second grid
electrode insulation layer, a first conductive pattern layer, an interlayer
insulation layer and a second conductive pattern layer, wherein the substrate comprises a thin-film
transistor region and a
capacitor region; the buffer layer is formed on the substrate; the
semiconductor pattern layer is formed on the buffer layer and comprises a source and drain
electrode region and a first electrode; the first grid electrode insulation layer is formed on the
semiconductor pattern layer and correspondingly covers regions, except the first electrode, of the thin-film
transistor region and the
capacitor region; the second grid electrode insulation layer is formed on the first grid electrode insulation layer; the first conductive pattern layer is formed on the second grid electrode insulation layer and comprises a grid electrode and a second electrode; the interlayer insulation layer is formed on the first conductive pattern layer; the second conductive pattern layer is formed on the interlayer insulation layer and comprises a source electrode and a drain electrode which are coupled with the source and drain electrode region as well as a third electrode. With the adoption of the array substrate and the preparation method thereof, the
capacitance of a
capacitor is increased, film layer structures of the regions except the capacitor region are not changed, the
signal line load is effectively decreased, and meanwhile, short-circuit risks of upper and lower film
layers of the grid electrode insulation
layers are reduced.