Abstract: Sedimentary faces and pollen study of Ash core in Aiby Lake with 14 C dating data gives information on the evolution of Aiby Lake since the last 2500 years. Sedimentary environment of the lake has been generally stable. But the lake level has oscillated with the influence of climatic ariation. It got a surface shrinking stage from about 400 to 300 BC. The area was much smaller than that of later high lake level stage. It was leas than 600 km² by referring present lake surface and the lake shoreline. The lake was surrounded with Haloxylon deserts. It run to a relative high lake level stage from about 300 BC to 300 AD, the end of East Zhou to West Jin Dynasty of China. Then the lake got to a high level stage from about 300 to 1400 AD, East Jin to the beginning of 15 th century. The lake level was at the height between 226 to 210 m above sea level, about 15 to 31 m higher than present lake surface. It means the environment of Aiby Lake region was obviously better than present during the Middle Ages. The lake level was in decreasing stage from about the beginning of 15 th to the middle of 17 th century, but the lake level was still higher than present lake level. Little Ice-age was Aiby Lake level rising stage from about middle 17 th to early 19 th century.
This study also supplies the information about changes of the historical salinityof the lake and natural burning around the lake.

Key words: Historical time, Environmental information, Pollen, Aiby Lake