成渝城市群作为长江上游重要的国家级城市群，地形差异显著、城市扩张迅速且极端降雨事件频发，洪涝影响呈现出复杂化、多源化特征。融合被动微波遥感降水数据、多源降雨资料、土地利用数据、夜间灯光及人口数据，构建“降雨-积水-不透水率-发展水平”的综合指标体系，从致灾因子、暴雨触发机制、地表水积聚过程和城市扩张模式等方面分析1995—2020年成渝城市群洪涝脆弱性的时空演变特征。结果表明：①1995—2020年成渝城市群洪涝脆弱性整体呈阶段性增强趋势，2000年和2020年为显著高值年份；②近30 a城市建设用地快速扩张（新增4 232 km²），以耕地转化为主，显著改变下垫面特性并加剧径流汇集；③极端降雨与地表积水强度在2000年和2020年明显增强，空间上形成“西南山地强触发-东部低洼易积涝”的分异格局；④洪涝脆弱性与城市发展水平呈非线性关系，重庆受益于地形条件及防洪工程建设，洪涝脆弱性有所降低，而成都及周边平原城市因快速扩张与不透水面增加脆弱性上升；⑤2020年新增城市建设区中约42%区域发生不同程度积水，部分平原城市新区受影响比例超过80%，表明快速扩张区域洪涝韧性不足。研究结果可为成渝城市群洪涝灾害防控及韧性城市建设提供科学依据。

[Objective] As a key national urban agglomeration in the upper Yangtze River Basin，the Chengdu-Chongqing urban agglomeration features pronounced topographic contrasts，rapid urban expansion，and increasingly frequent extreme rainfall events，resulting in highly complex and multi-source flood impacts. [Methods] This study integrates passive microwave remote sensing precipitation data，multi-source rainfall datasets，land-use data，nighttime light imagery，and population data to construct a comprehensive indicator system comprising precipitation，waterlogging，impervious surface ratio，and development level. From the perspectives of hazard factors，rainfall triggering mechanisms，surface water accumulation processes，and urban expansion patterns，the spatiotemporal evolution of flood vulnerability in the Chengdu-Chongqing urban agglomeration from 1995 to 2020 is systematically analyzed. [Results] （1） Flood vulnerability exhibited a staged increasing trend during 1995-2020，with significant peak years in 2000 and 2020；（2） urban construction land expanded rapidly over the past three decades （an increase of 4，232 km²），mainly through the conversion of cropland，which significantly altered surface characteristics and intensified runoff concentration；（3） extreme rainfall and surface waterlogging intensity increased markedly in 2000 and 2020，forming a spatial pattern of “strong triggering in southwestern mountainous areas and easy waterlogging in eastern lowlands”；（4） flood vulnerability shows a non-linear relationship with urban development level—vulnerability decreased in Chongqing due to favorable terrain and enhanced flood control infrastructure，whereas it increased in Chengdu and surrounding plain cities due to rapid expansion and increased impervious surfaces；（5） approximately 42% of newly developed urban construction areas experienced waterlogging in 2020，with some plain cities exceeding 80%，indicating insufficient resilience in rapidly expanding areas. [Conclusions] Urban flood vulnerability is not solely determined by the level of development； rather，it is jointly influenced by topographical conditions，patterns of urban expansion，and engineering regulation capabilities. The Chengdu-Chongqing urban agglomeration faces compound flood processes involving both basin-wide floods and urban waterlogging. Therefore，measures should be taken to improve flood control and drainage standards，optimize urban spatial structures，strengthen sponge city initiatives，and enhance coordinated regulation between upstream and downstream areas within the urban agglomeration.These findings provide scientific support for flood disaster mitigation，vulnerability reduction，and resilient urban development in the Chengdu-Chongqing urban agglomeration.