Water security is related to the coordinated development of all aspects of urban society and economy. Taking Taizhou city as an example, this paper establishes the evaluation index system of water security by using PSR model. The index weights was obtained by the analytic hierarchy process and the safety degree of each index was acquired based on the principle of diminishing marginal benefit, and the comprehensive index method was used to evaluate the water security of Taizhou city from 2011 to 2015.The results show that the water security situation is in a safe state, and chemical oxygen demand, annual rainfall, river pollution percentage, and urban water reuse rate are the main influencing factors of water security. We also predicted the future water security of Taizhou city by using the Grey Prediction GM (1,1) model. The forecasting results show that the water security status of Taizhou from 2015 to 2020 is still in a basic safety state, and the trend is increasing year by year to the full safety state.