In the framework of national project coded KC. 09. 03/06-10, the study on the relationship between environmental factors to the development of cell density of phytoplankton communities in Quang Tri coastal zone had been carried out in the wild from June 2007 to May 2005, by resrarchers of Institute Marine and Environment Resources. Although, the study also pointed out, the concentration of nitrate, nitrite, am in iac, phosphate and silicate salts were rather high, over limit level of ASEAN from 1 to 3 times, but no eutrophication of phytoplankton occured in waters, especially coastal stations. On the other hand, some results of research by software Primer V6 also for similar resul!s with the initial receipt of the relationship between development density of phytoplankton communities in Quang Tri and environmental factors in this areas.