To solve the increasingly serious problem of water environment, it is of great significance to monitor chemical oxygen demand (COD) of water as the early warning of water pollution. Based on the principle of ultravioletvisible spectroscopy to measure the water quality parameter COD, the collection and transmission system of water COD monitoring information in a large area is studied by combining the wireless sensor network (WSN) technology with spectral COD monitoring technology. Based on the Coxtex-A7 hardware platform, the data compression and WSN is utilized to realize wireless real-time monitoring of water COD. The experimental results show that the system can achieve collection and effective and reliable transmission of water COD monitoring data. This system does not only have the characteristics of low power consumption, wide coverage area, fast response, and easy maintenance, but also provides a basis for the comprehensive analysis of water environment in a water basin.