Abstract: Abstract: The water quality environment of aquaculture water is the basis for the survival of aquatic animals. Water quality factors such as temperature, pH value and dissolved oxygen are the key factors affecting aquaculture water quality. Therefore, timely monitoring of water quality has important practical significance for high yield, health and safety of aquaculture. In order to promote the development of aquaculture informationization, it is necessary to monitor aquaculture ponds more accurately and conveniently. This paper designs a water quality monitoring system based on NB- IoT narrow-band Internet of Things technology. The single hop distance of this technology can reach thousands of meters. It is more suitable for parks, aquaculture ponds and other places in terms of communication range, deployment number and environmental applicability of nodes. The technology solves the problems of insufficient network coverage, high terminal power consumption, insufficient terminal equipment and high comprehensive cost in aquaculture area. The system specially designs terminal sensor nodes, background control module, monitoring application software and hardware. The functions of data storage and remote collection of multi-sensor node information such as temperature, pH value, dissolved oxygen and other sensor nodes were realized, as well as the intelligent control of aquaculture pond aerator. Temperature, pH value, dissolved oxygen and other water quality information were collected and coded by STM32L151C8 MCU and sensor terminal in real time. First, data was reported to cloud platform through NB module and core network. The application layer called the query interface in time to realize online remote monitoring of aquaculture ponds. Then, the system used the Internet of Things Telecom Cloud Platform, which was equipped with a Profile file that described the functions of the device and a codec plug-in that analyzed the protocol package, to stores the water quality parameter data in time. Finally, the binding of NB module devices was completed. The NB wireless communication module data format and data transmission were realized by Keil tool. Java was used to develop background monitoring applications for accessing cloud platforms, controlling underlying devices, and local data processing. Monitoring applications could not only send HTTP requests to monitor cloud platform data, but also send commands to terminal control module to control the start and shutdown of aerators. The experimental results showed that the system could acquire water quality information in time, such as temperature, pH value, dissolved oxygen and so on. The control accuracy of temperature, dissolved oxygen and pH value were kept in the (0.12 ℃, (0.55 mg/L, and less than 0.09, respectively. The average relative errors were 0.15%, 2.48% and 0.21%, respectively. Monitoring applications could also issue commands to cloud platforms to control aerators at any time. The codec plug-in of the platform encoded the command and send it to the hardware terminal. The response time of the remote control device was less than 100 ms, and the whole system was stable, which proved the reliability of NB- IoT technology. Data transmission is timely and accurate, which can meet the actual production needs and provide strong data and technical support for further water quality control and aquaculture production management.