According to the characteristics of urban rivers, considering the hydrology conditions and socioeconomic conditions, setting out from the important factors that affects the vulnerability, this paper presents a Vulnerability Assessment System established for urban rivers, researches the vulnerability of different reach, so as to provide reference for use and protection of urban rivers. Several appropriate evaluation indexes are chosen to analyze the vulnerability level of the Chanba River by Matter-element Analysis Theory, and use rough set theory to determine the weight. The results indicate that the MA Du-wang and Chang Jia-bay, where is located in the eastern suburb of Xi'an and is affected greatly by human factors, have the highest vulnerability, other places have medium vulnerability.