The investigation of phytoplankton community characterization including species composition,population size,dominant species and saprobic indicators was conducted in order to evaluate the water quality of Majia and Tuhai River in Haihe River basin.The results revealed that 126 species of phytoplankton belonging to 7 phyla and 67 genera existed in Majia River,while 114 species of phytoplankton belonging to 7 phyla and 63 genera were found in Tuhai River.Chlorophyta was the richest algae in both rivers,followed by Bacillariophyta and Cyanophyta.Cyanophyta,Chlorophyta and Bacillariophyta were found in all the sampling sites (the frequency was 100%).Cyanophyta was absolute the majority in Majia River in population,which accounted for 53.59%,while the Chlorophyta was predominant in Tuhai River,which accounted for 35.73%.The average density of phytoplankton in Majia and Tuhai River were 22.424×106 ind./L and 13.950×106 ind./L,respectively.The Shannon-Weaver index,Margalef index and Pielou index varied among 2.48-4.64,3.62-9.91 and 0.47-0.84 in Majia River,while 3.04-4.57,2.94-10.15 and 0.63-0.82 in Tuhai River,respectively.The water quality of both rivers was preliminary evaluated based on above results.In conclusion water quality was good,can be labeled as mesotrophic,but had the potential to turn to eutrophication.So we should pay attention to protect the water quality and enhance the management of the both rivers.