Abstract: In 1972. It was discovered by earth resources satellite of USA that Lop-Nur. which is known as a big ear shaped of in west China had dried up. Anyhow in the geological peroid. Lop-Nur was a big lake of 2×10⁴², even before the 1958. It covered an area of 2 919 km². In or-der to set up the Lop-Nur Nature Reserve. We went to Lop nor area for five times from 1995 to 1997. In the spring of 1996, we reached Loulan Ancient city from the center of Lop-Nur and carried out the researches on the Lop-Nur and its environment.It was found that in historical period. Lop-Nur has become rich in water, and then with-ered, even dried up for many times. But In modern times, it was not a wandering lake but the salt converging depression of Tarim Basin. As for this point a large area of deep salt rock precip-itated at the center of former Lop-Nur. Tarim River has Changed its route for many times, but it only resulted in the changes in shape of water-surface at the mouth of Tarim River.The area of Lop-Nur has withered for many times, which was related to the development of agriculture in history. About 1400 a BP. and evident withering took place, which was resulted from the route change of Tarim River and cause the ruin of Loulan Ancient city. The drying-up of Lop-Nur in mordern times is the outcome of human influence.In satellite image, there are six evident traces in ancient Lop-Nur and four traces after 1921 can be seen.In consideration of arid climate and human economic development in Tarim Basin the situa-tion of drying-up and desertification can not be changed.

Key words: Lop-Nur, history, environmental changes