In　order　to　solve　fuzziness　of　the　water　quality　evaluation　and　incompatibility　of　water　quality　index,　an　assessment　method　of　groundwater　quality　was　proposed　based　on　the　projection　pursuit　method　with　the　firefly　algorithm　(FA)　for　the　diversity　of　water　quality　evaluation　index.　Based　on　the　classification　standard　of　groundwater　environment,　the　projection　index　function　which　could　reflect　the　water　quality　of　groundwater　was　established,　and　the　firefly　algorithm　was　adopted　to　optimize　the　projection　index　function　for　obtaining　the　best　projection　direction　of　projection　index　function　and　calculating　the　value　of　best　projection　direction,　thus　the　groundwater　could　be　assessed　comprehensively.　The　groundwater　of　Chao　Yang　District　in　Beijing　as　the　research　object　was　comprehensively　evaluated　with　this　method.　The　evaluation　results　of　the　assessment　method　was　compared　with　ones　of　the　comprehensive　scoring　method　(F　method),　the　single　factor　evaluation　method　and　the　projection　pursuit　method　with　the　real　coded　accelerating　genetic　algorithm　(RAGA-PP).　The　results　of　application　example　approved　that　the　assessment　method　is　reasonable　and　feasible,　and　can　be　available　for　assessment　of　groundwater　quality.　©,　2015,　China　University　of　Mining　and　Technology.　All　right　reserved.