Lancang - Mekong River is an important international river in south - east Asia, which flows through sixcountries. Lancang River Basin is rich in natural resources and wildlife, most part of the basin is the naturalconservation area of rare and endangered animals and plants in China. Hie basin area is still an undevelopedregion at present. However, due to deforestation and pollution from industrial, agricultural and domestic sec-tors, water quality of the river has been deteriovating in resent years.In this paper, the author has analyzed present water quality status of Lancang River both in mainstreamand its tributaries based on the data during 1990-1997. The results have shown that water quality status ofthe river is not good enough although industrial estates are not many in the region. The pollutants of the riverare mainly organic matters. The main pollution sources are wastewater from paper plant, sugar plants, domes-tic wastewater from Dali City and Jinghong City, as well as fertilizers and chemicals from agricultural fields.Heavy metals from Lanping Lead & Zinc Mine and Lancang Lead Mine are main pollutants in the tributaries ofBijiang River and Nanlan River. Water quality of the mainstream is better than its tributaries. It is better indry season than in rainy season in the river.The author thinks that pollution control in the basin should be down as soon as possible to improve waterquality. Some measures should be taken to reach the goal. They are the population control, wastewater treat-ment to reach the emission control standard, water quality monitoring enhancement and so on.