The invention relates to an automatic irrigation system, which comprises a main control device, multiple irrigation pipelines, an electromagnetic valve device, a sensor device and a wireless communication device, wherein the sensor device is arranged on a piece of land requiring irrigation; a water pump is arranged on each irrigation pipeline, and is positioned at one end close to a water source; a pressure gauge is arranged in each irrigation pipeline, and is positioned at one end close to an irrigation sprayer; the pressure gauges are connected with the main control device; the main control device controls the water pumps to open or close as per high and low water pressure values from the pressure gauges; the main control device is in wireless communication with a control mobile phone and the internet. The automatic irrigation system has the benefits as follows: the system can be controlled manually or automatically, and a more accurate effect can be obtained through combination of the two control manners; the manner that one water pressure control device is matched with one irrigation pipeline is adopted, so that the energy is saved on one hand, and the impact on the pipelines by high water pressure can be reduced and the pipelines are protected on the other hand.