The invention relates to a soil humidity sensor network system and a method for acquiring soil humidity information, which belong to the technical field of wireless sensor networks. In order to realize the effective acquisition of the soil humidity information in farm fields, the invention provides a soil humidity sensor network system based on interval adjustment, which comprises soil humidity sensing equipment, data collection equipment, data teletransmission equipment and system management equipment. After the system and the method are adopted, the network size can be enlarged effectively and transmission data can be pressed effectively according to application requirements and the sensing accuracy of an external sensor, so unnecessary resource waste is avoided and the optimization of the sensor networks is realized based on application. The practical application proves that the system and the method can cooperate with an irrigation system better to achieve the good effect of automatic irrigation.