Currently, water quality monitoring in China is faced with many problems, such as limited monitoring points, heavy communication costs, and high power consumption. To solve these problems, this study constructs a water quality monitoring system based on the LoRa wireless transmission technology. This system is composed of a data acquisition terminal, a wireless communication circuit, and a remote-control center. The embedded technology and the FreeRTOS system are used for sensor task scheduling and data collection. The processed data are then sent to the remote-control center through a wireless communication circuit with the LoRa technology and finally displayed in the upper computer software, which, implemented in Qt, can monitor sensor status and location of monitoring points in real time. The test results show that the coefficients of variation of the five data including pH are less than 5% and that of temperature is as low as 8.76%, which means the water quality of the Bahe River can be monitored stably and continuously for a period of time. With the advantages of low cost, strong expansibility, and high integration, the proposed system has good application prospects in water environments of sewage monitoring and aquaculture.