Tangnaihe hydro-station is one of major controlling station of the Yellow river in Qinghai province. The average annual runoff through the hydro-station is 2. 0×1010m3

with 34. 5 %of the annual runoff 5. 8×1010m3 of Yellow river and 91. 0%of the runoff in the main aspect among the Qinghai province. The place beyond Tangnaihe is one of the major water supply and conserving area for the Yellow river. Through analyzing statical character of runoff and sediment across the station from 1919 to 1999

the years that low and partial low flow year appeared frequently were in the 1920' s and 1990' s

and the years that high and partial high flow year appeared frequently were in the 1940' s

1960' s and 1980' s. Changes of annual sediment mainly depended on annual runoff

they changed synchronously and were significantly related with each other. The decrease of runoff and sediment on the mainstream of the Yellow river in 1980' s was mainly due to periodic changes of annual runoff. And 1990' s belong to a partial high flow period. Compared with low and high flow degrees in history

the partial low flow period in 1990' s is normal. Changes of annual runoff on the Yellow river in Qinghai province have not developed towards decline

and changes of runoff and sediment were stable.