Abstract: The Third Member of Nenjiang Formation is located in the Xinzhan area, the southwestern part of Songliao basin. According to the changes of sporopollenalga assemblages from bottom to top，seven sporopollenalga assemblages were recongnized for the Third Member of Nenjiang Formation，which can indicate the salinity changes of water body of the take. They are （in ascendling order）：CyathiditesPinuspollenitesDinogymniopsis assemblage which indicates a brackish lake environment with a shrinking water body，DinogymniopsisLeiosphaeridiaPinuspollenites assemblage which indicates a slightlysaltied lake environment with a enlarging water body，CicatricosisporitesPinuspollenitesBotryococcus assemblage which indicates a freshwater to slightlysaltied lake environment with a shrinking water body，DinogymniopsisChlamydophorellaTaxodiaceaepollenites assemblage which indicates a shallow lake environment transforming from freshwater to brackish water frequently, CicatricosisporitesPinuspollenitesPediastrum assemblage which indicates a freshwater lake environment with a reducing water body，NenjiangellaBalmulaCyathidites assemblage which indicates a freshwater lake environment with a broad water body，and CyathiditesTrilobosporitesBotryococcus assemblage which indicates a brackish lake environment with a shrinking water body.

Key words: sporopollen, dinoflagellates, environments, Nenjiang Formation, Xinzhan area, Songliao basin