Assessment of water resource vulnerability for identifying where water resources are potentially more vulnerable to adverse effects is a pre-requisite to take adaptation strategies. This study proposed a method for water vulnerability evaluation as a function of sensitivity to climate change, people per flow unit of one million cubic meters per year, water use to availability ratio, and per capital water use. Take the Hai  River basin, the most water scarcity region in China, as an example. The vulnerability of water resources under current situation and 3 different scenarios in 2050 are evaluated. Results indicate that the plain area suffer from more serious vulnerability than mountain area; although the Hai River basin is predicted to become more moisture, vulnerability of water resources may get no improvement in the future because of the increase of water withdrawal as population and economy continue to grow.