Based on the basic principles of DPSIR model, following the principles of construction of evaluation system, starting from the truth about water resources and water environment in Tianjin, and taking five indicators, including driving force, pressure, status, etc. , as the criterion layers, 20 indicators, including population density, wastewater emissions, total water resources, urban water compliance rate, etc. , are selected to evaluate water environment security situation of Tianjin City during 2009 and 2011. The results show that, water environment security situation was the most promising in 2009, followed with which in 2011, while it was the worst in 2010. Although the level of water environment security was fine, the increasing population density and waste water emissions, with other environmental factors threatening urban water security, can not be ignored. Thus urban water environment problem remains to be solved.