The study was undertaken from August to December in 2006.18 saline lakes and 3 subsaline lakes in Ali region,Tibet,had been investigated.The salinity ranged from 0.31 g/L to 300.71 g/L.44 biological samples and 22 hydrochemical samples were collected.One hundred and five species of phytoplankton and fourteen species of zooplankton,belonged to forty nine and eleven genera respectively,were identified.Diatoms were dominant in species richness by 60 percentage.Metadiaptomus asiaticus Uljanirs was reported firstly in Tibet.Spirulina spp.,Dunaliella salina,Daphniopsis tibetana Sars,Artemia spp.distributed in 8,3,5 and 12 lakes,respectively.No plankton was identified in Cabu Co and Jeze Chaka because of high salinity and(or)some unknown factors else.Plankton species richness decreased as salinity increasing.The correlationship between plankton species richness and salinity was not significant(r2=-0.05,p>0.05)with salinity ranged from 0.31 g/L to 300.71 g/L,according to statistics.This paper showed a view to explain the seasonal population change between Daphniopsis tibetana Sars and Copepoda.The result suggested that diatoms,such as cyclotella spp.,played an important role to this phenomenon.Some advices on the exploitation of saline lake bioresources,especially Daphniopsis tibetana Sars,were given at the end.