The existing assessment methods for voltage vulnerability in power systems suffer the drawback that it is difficult to present a full view while the weight-based integrated indices are too subjective.By referring to certain representative voltage stability indices and the information of bus significance，a multi-criteria integrated assessment for voltage vulnerability and the corresponding integrated index，namely，the relative voltage vulnerability index，are proposed based on data envelopment analysis.The examination of outliers is also taken into account to improve the proposed method.Finally，the power grid of Jiangxi Province is used for case study to demonstrate the comprehensiveness，effectiveness and objectivity of the proposed method and index.