The invention provides an irrigation system applicable to a plateau mountainous area, which comprises a diversion system, a water storage system and an irrigation system, wherein the diversion system comprises a reservoir (1) or a stream (2) and a primary water conveying pipeline (4a) communicated with the reservoir (1) or the stream (2); the water storage system comprises a water storage pool (3), a water cellar (5) and a secondary conveying pipeline (4b) for connecting the water storage pool (3) with the water cellar (5); the primary water conveying pipeline (4a) is communicated with the water storage pool (3) and the reservoir (1) or the stream (2); the irrigation system comprises a micro-sprinkler irrigation system (6) or a drip irrigation or filtration irrigation system (7); the micro-sprinkler irrigation system (6) or the drip irrigation or filtration irrigation system (7) is connected with the water storage pool (3) or the water cellar (5) through a three-stage water conveying pipeline (4c); the height of the reservoir (1) or the stream (2) is larger than that of the water storage pool (3); and the height of the water storage pool (3) is larger than that of the water cellar (5). By using the invention, the water of water source fields can be conveniently led out by means of physiographic relief, the water also can be effectively stored, irrigation is facilitated and water sources are saved.