In order to satisfy the needs of agrometeorological observation, a soil moisture detection system using frequency domain reflectometry (FDR) was designed. It includes FDR sensors, data acquisition and remote data management. The FDR measurement is based on transmission theory and resonance circuit, and data acquisition part takes full account of signals anti interference ability and error correction methods. Data measured are transferred to central database in wireless communication mode first, and then are sent back to local stations through Internet. Results show that this system can run continuously and stably. Data revised are close to that from drying method. Errors less than 2% tell that this system can totally meet the needs of agrometeorological observation.