(1) During spring and summer, the most popular drink is "Airag", fermented horse milk. The Russians call it "Koumiss".

(2) Koumiss transmits wildness, boldness and hospitality of Mongolian, Qingke barley beer ferments simple character of the Tibetan.

(3) Organic acids in koumiss had apparent inhibitory effect to bacillus subtilis, in them, lactic acid was most important whereas acetic acid and alcohol had synergistic effect.

(4) This paper introduced koumiss making method in different parts of ancient times. It is of great importance to study, develop and utilize the resource of mare milk in China.

(5) In this paper, 39 strain yeasts were isolated from 4 samples of koumiss. Generic Identification was conducted through Morphology and biochemistry.