Abstract: To study the effect of the brine discharged from desalination plant on the distribution of salinity in Jiaozhou Bay,a numerical model for the salinity diffusion in the Jiaozhou Bay is set up based on the POM model. With the inputting conditions of existing desalination volume and the near future volume planning in 2010,the distributions and changes of the salinity in the bay are simulated. The results show that in February,May,August and October in 2010,the averaged salinity of the bay is 30.989 5, 30.80.0,30.022 1,and 30.230 6,respectively,which have an increasing about 0.027 6,0.027 42, 0.02121,and 0.020 48 than in 2008. The salinity of the local areas close to the brine discharged locations will change obviously,such as in the area near Huangdao plant,the seawater area with the salinity above 31.55 in 2010 is 0.24 km² larger than 200.in February high tide,and the seawater area with the salinity above 32.00 turns up,It is 0.08km²;The seawater area with the salinity above 31.55 in 2010 increases 0.24 km² than 2008 in February ebb tide,and the area with the salinity above 32.00 increase about 0.16 km². The highest salinity values reached 40.23,36.66,37.94,37.87 in February,May,August and October respectively. Coupling with the preliminary laboratory results,we can see that in February the highest salinity is higher than 38.62,which is the no-detected toxic concentration of the brine on the phytoplankt on community in the Bay. This shows that in 2010,the brine discharged from the desalination plants will have a little effect on the distribution of average salinity in the whole bay,but it will lead to a marked increasing in salinity near to the area of the desalination plants,and will have a certain extent effect on the growth of the phytoplankton.