Urban　flood　disasters　exhibit　chain-　like　propagation　characteristics,　and　analyzing　the　transmission　laws　and　spatiotemporal　evolution　features　of　urban　flood　disaster　chains　is　of　significant　importance　for　disrupting　the　disaster　chain.　This　study　aims　to　use　two　events　from　the　＇7·20＇　unprecedented　heavy　rain　and　flood　disaster　in　Zhengzhou—the　flooding　of　metro　line　5　and　the　flooding　of　the　Beijing-　Guangzhou　expressway　tunnel—as　case　studies.　A　knowledge　graph　was　constructed　to　reveal　the　transmission　laws　of　the　disaster　chain.　By　reviewing　the　evolution　process　of　the　disaster　chain,　triggering　points,　detonation　points,　diffusion　points,　and　amplification　points　within　the　disaster　chain　were　identified.　The　study　focused　on　analyzing　the　disaster-causing　mechanisms　and　spatiotemporal　characteristics　of　the　disaster　chain,　presenting　the　impact　levels　of　different　disaster　chains　in　the　form　of　disaster　curves.　Analysis　of　typical　cases　of　the　＇7·20＇　flood　disaster　in　Zhengzhou　indicates　that　there　were　several　chances　to　break　the　disaster　chains　in　both　events.　In　the　disaster　relief　process,　the　influence　of　predisaster　and　in-　disaster　factors　should　be　comprehensively　considered,　and　decisive　measures　should　be　taken　to　break　the　chain.　It　is　crucial　to　fully　leverage　the　timeliness　of　emergency　measures,　promptly　block　detonation　and　diffusion　points,　and　reduce　losses　from　flood　disasters.　This　method　can　be　applied　to　the　retrospective　analysis　of　chain-like　disasters,　guiding　the　analysis　of　the　disaster-　causing　mechanisms　and　entry　points　for　disaster　relief　in　specific　events.　©　2024　International　Research　and　Training　Center　on　Erosion　and　Sedimentation　and　China　Water　and　Power　Press.　All　rights　reserved.