Ma,　Y.;　Cao,　H.;　Zhang,　L.,　and　Fu,　Z.,　2020.　Relationship　between　local　government　competition,　environmental　regulation　and　water　pollutant　emissions:　Analysis　based　on　mediating　effect　and　panel　threshold　model.　In:　Yang,　Y.;　Mi,　C.;　Zhao,　L.,　and　Lam,　S.　(eds.),　Global　Topics　and　New　Trends　in　Coastal　Research:　Port,　Coastal　and　Ocean　Engineering.　Journal　of　Coastal　Research,　Special　Issue　No.　103,　pp.　511-515.　Coconut　Creek　(Florida),　ISSN　0749-0208.　Water　has　been　further　polluted　by　＂development　at　the　cost　of　environment＂　since　the　reform　and　opening　up.　The　emission　of　water　pollutant　in　China　is　closely　related　to　political　economy,　and　local　government　competition　is　an　important　factor　in　pollution　control.　This　paper　specifically　studied　direct　and　indirect　effects　of　local　government　competition　on　environmental　pollutant　emissions,　and　tested　the　nonlinear　relationship　between　local　government　competition　and　water　pollutant　emissions.　The　results　show　that　local　government　competition　has　been　characterized　by　＂race　to　the　top＂,　which　has　direct　and　indirect　effects.　Formal　environmental　regulation　plays　a　mediating　role　in　the　process　of　local　government　competition　affecting　water　pollutant　emissions,　but　informal　environmental　regulation　does　not　play　such　a　role.　With　increasing　formal　environmental　regulation,　local　government　competition　is　playing　a　bigger　role　in　suppressing　water　pollutant　emissions.　©　Coastal　Education　and　Research　Foundation,　Inc.　2020.