Abstract: To determine the impacts of meretrix activity on the total nitrogen and total phosphorus of seawater and sediment and the microbial indicators which can indicate these impacts,we did buried meretrix impoundments of field experiments and indoor simulation experiments.We set experimental pond(which was put some meretrix) and control pond(which wasn't put any meretrix) near the high tideline of estuary of Shuangtaizihe in August of 2009.Then four seasonal samples (which both from the experimental pond and the control pond) were collected in August,October,December of 2010 and May of 2011,then we chosed some main microbial activity indicators (including the microbial biomass carbon,microbial basal respiration,the total number of bacteria,nitrifying bacteria and denitrifying bacteria number),as well as its total nitrogen(TN) and total phosphorus(TP) as the measurement indicators to know the impacts of meretrix activity on the TN and TP of seawater and sediment.By correlation analysis to determine which microbial indicators can be used to indicate the TN and TP impacted by the activity of meretrix.At the same time,we also did the indoor simulation experiments.By the comprehensive analysis of the field experiments and the indoor simulation experiments,we found that the TN,TP in seawater was significantly reduced after putting meretrix and the total number of bacteria in both seawater and sediment were decreased,indicating that meretrix play a role in mitigation of eutrophication.In addition,we found that the total number of bacteria in both seawater and sediment and microbial biomass carbon were all significant correlated with TN and TP,so we can use these microbial indicator to indicate the impact of meretrix activity on the TN and TP.