To　find　out　the　relationship　between　industrial　agglomeration　and　environmental　pollution,　this　paper　carried　out　empirical　research　on　the　panel　data　collected　from　271　prefecture-level　cities　in　China　from　2004　to　2017　through　a　spatial　panel　econometric　model.　It　reviewed　the　influence　of　agglomeration　externality　on　environmental　pollution.　The　results　detected　an　inverted　＂U＂-shaped　relationship　between　manufacturing　industry　agglomeration　and　environmental　pollution　nation-wide.　The　manufacturing　industry　agglomeration　level　at　the　inflection　point　was　0.652,　suggesting　that　prefecture　level　cities　suffered　severe　environmental　pollution　problems.　At　the　regional　level,　the　manufacturing　industry　agglomeration　in　eastern　and　western　China　had　a　significant　adverse　effect　on　environmental　pollution.　In　the　central　China,　the　relationship　between　manufacturing　industry　agglomeration　and　pollution　was　＂N＂-shaped.　The　manufacturing　industry　agglomeration　levels　in　most　prefecture-level　cities　were　between　the　two　inflection　points.　The　environmental　pollution　aggravated　as　the　manufacturing　industry　agglomeration　level　rose　in　the　range.　As　for　cities　in　the　northeastern　region,　manufacturing　industry　agglomeration　has　no　direct　causal　relationship　with　environmental　pollution.