The　biofilms　generated　in　a　fire　extinguishing　water　supply　system　can　cause　corrosion　and　a　reduction　in　the　water　supply　capacity;　thus,　degrading　the　system　performance.　To　mitigate　microbial　corrosion,　appropriate　disinfection　measures　are　necessary.　In　this　study,　the　secondary　addition　of　chlorine　is　employed　to　investigate　the　kinetics　of　chlorine　decay,　and　shock　disinfection　is　applied　to　investigate　the　removal　efficiency　of　corrosion　bacteria,　and　the　microbial　composition　of　a　biofilm　on　the　pipe　wall　was　also　clarified.　The　results　show　that　the　residual　chlorine　content　in　the　secondary　chlorination　process　was　directly　correlated　with　the　decay　rate　of　residual　chlorine　and　the　corrosion　rate　of　the　pipe　wall.　Additionally,　the　chlorine　impact　disinfection　method　could　reduce　the　electrochemical　corrosion　phenomenon　of　the　pipe　wall.　When　the　concentration　of　chlorine　was　3　mg/L,　the　removal　rate　of　corrosion　bacteria　was　higher　in　60　min　than　in　30　min.　Specifically,　most　of　the　bacteria　were　inactivated　in　60　min　and　the　biofilm　was　severely　damaged.　Shock　disinfection　could　significantly　inactivate　all　microflora　in　the　biofilm;　the　relative　abundances　of　microflora　varied　significantly,　while　the　change　of　microflora　at　the　phylum　level　was　insignificant.　This　study　can　provide　theoretical　support　for　the　secondary　addition　of　chlorine　and　shock　disinfection　in　a　fire　extinguishing　water　supply　system.