Abstract: Qinghai Lake is situated in northern-east of Qing Zang plateau (36°32'-27°5'N. 99°36'-100°47'E.), at an altitude of about 3300m, covering an area of 4635 km². This saltwater lake is the bigest inland water in China, of which the salty content is about 14.383 g/ml. It's water plants, however, is still little known. This report is based on a collection by the author in 1982,All Cyperaceae plants found in this lake are enumerated, and keys to genera and species are provided. 8 new species belonging to both genera are described. They are as follows:1. Physical condition of Qinghai lake; 2. The key of genera and species of Cyperaceae; 3. Description of new species; 4. Distribution, growth and development of Cyperaceae.