Submarine groundwater discharge (SGD)with inputs of nutrients and water into the ocean in certain re-gions plays a significant role in coastal material fluxes and their biogeochemical cycle,which cannot be ignored for its impact on the eco-system.In this paper,SGD into the typical aquaculture base of northern China,Sanggou Bay,was estimated using naturally occurring radium isotopes,223 Ra and 224 Ra.Results showed that the radium ac-tivities of submarine groundwater,especially in the pore water [224Ra= (968±31)dpm/(100 L),223Ra= (31. 4± 4. 9)dpm/(100 L),n= 9],were obviously greater than those in the surface water [224Ra= (38. 7±2. 0)dpm/(100 L),223Ra= (1. 70±0. 50)dpm/(100 L),n= 21].Assuming steady state and using a radium mass balance model with sources and sinks,the SGD rate was estimated to be among (0. 23~1. 03)×107 m3/d.SGD flux var-ied from spring tide to ebb tide.During spring tide,SGD flux was smaller because of weak hydraulic gradient while it was much larger during ebb tide because of strong hydraulic gradient.During a tidal cycle,the SGD flux was averaged to be 0. 39×107 m3/d based on 223Ra and 224Ra.Tidal-driven SGD can account for 61%of the total SGD.Therefore,the main driving force of SGD into Sanggou Bay was tidal pumping and SGD of Sanggou Bay in coastal zone contributes a lot to seawater composition and material exchange between land and sea.