Abstract: The impacts of underwater explosion on water quality including 10 indexes(Secchi disk,salinity,dissolved oxygen,pH,suspended matter,petroleum,ammonia,nitrate,nitrite,and available phosphorus)and plankton including 3 indexes(Chl a,phytoplankton biomass,and zooplankton biomass)were monitored within 1000 meters and 2 h of the explosion at coastal Dagushan area in Dalian bay from September to December in 2007. The results showed that there were significant impact of explosion on transparency and suspended matter,while there were no significant impact of explosion on the other indexes.Overall,it was not found that there was obviously impact of the explosion on the water quality and the biomass of plankton at coastal Dagushan area.