Abstract: This paper has studied the growth rhythm, dry weight of grasses of seven species and relationship between factors of environment. The quality of grasses in Kobresia humilis meadow, which is main vagetation type of Qinghai Xizang plateau, is excellent, so they occupy a very important place in animal husbandry. The results are as follows:The distribution is an aggregated dispersal on grasses of seven species in Kobresia humilis meadow. The number of individual tillers after green up increases with increase of precipitation, sunshine time and accumulated tem, greater than 3℃ and reaches peak in early booting period.The critical value of low tem. is 3℃ for growth of grasses population. The populations begin to bud bursting at average daily air tem. ≥3℃.The course of development become quickly at average daily air tem. ≥ 5℃. The aboveground dry weight of an individual after green up begins to increase with increase of≥5℃, ≥10℃ accumulated tem. and precipitation. The dry weight is biggest at late August or early September.The populations need about 134 days from green up to ripeness of seed. In this period, the accumulated tem. of≥ 5℃ is about 949.7℃; accumulated tem. of≥10℃ is about 485.6℃; sunshine time is about 812.0 hours, amount of accumulated precipitation is about 324.9mm. The primary factor affecting growth is temperature (p<0.01) , and the second is precipitation and water content of soil (p<0.01)