Abstract: From 250 thousands year ago to 1900's, the water surface of AiBi Lake decreased from 300 km² to 1310 km² , decreasing averagely 0.07 km² ／y. During 1950's－1980's, the Lake areas decreased rapidly from 1200 km² to 522 km², averagely deereasing 21.2 km²/y, which is 300 times decreasing speed than that during 250 thousands years ago. Since 1949, the Lake areas has been decreased 2.25 km² averagely when one mu wasteldround was openedup. The main factars of decreasing Lake area is opening up wasteland and irrigating by Lake water (85%) ；forest and plant to be destroied (10%) ；The drought fluctuation of atmospheric circulational periodic changing (2%-5%).
The declining of AiBi Lake has Cased a intense effect on ecologic environment in this region . So a affective protect measure to AiBi Lake should be performed.