Abstract: The hydrological telemetry system based on ADuC845 is developed. The system is divided into two parts: the telemetry instrument and the host. The telemetry instrument collects the water level data and then transmits them to the host by GSM. When the data exceeds the limit, the host will report the alarm promptly, and at the same time, the parameters such as the collection time interval and the host number are set by the two modes of the host and the mobile phone, and the operation is flexible and simple, which greatly enhances the adaptability. After on-site debugging, on the one hand, the communication of instrument is good, the data is accurate, and on the other hand, it has a friendly human-computer interaction interface, which has reached the expected goal.