Effective monitoring of urban sewage treatment is very important for environmental protection and public health. In this paper, a sewage monitoring system based on the Internet of Things is proposed. With the Internet of Things as the main method, the system architecture is discussed, and the system implementation process is introduced. Finally, a series of experiments is designed and implemented to evaluate the differences between the proposed monitoring system and the traditional wired communication monitoring system in key performance indicators. The results show that the highest response time of the sewage monitoring system based on Internet of Things is only 164 ms, the highest system failure rate is only 2.5%, and the energy efficiency ratio is above 0.83. The comprehensive experimental results show that the sewage monitoring system based on the Internet of Things shows advantages in key performance indicators, which proves its potential application value in the field of urban sewage treatment monitoring.