With the rapid development of social economy, the city's infrastructure must be continually improved. Using waterworks automation system as an example, its relationship to the social development and the vital interests of the masses, if difficult to maintain in the operation of the reliability and security, will be difficult to play its proper role. Under this background, the study found through practice, introducing PLC which can make the automation system more perfect. This paper takes some tap water in waterworks automatic control system in our country as an example, the introduction of PLC to the overall design of automation system and the analysis of process control.