Abstract: The authors observed Blue Sheep ( Pseudois nayaur) population in the Helan Mountain , Ningxia Province in November 1994 ,between J uly and Nevember 1995 ,respectively. It was found that the Blue Sheep preferred to elevation of 1800～2000 m in Helan Mountain. The Blue Sheep foraged primarily in the morning and at dusk. Of the 448 individuals observed ,the average herd size was 5. 5 individuals. The Blue Sheep were frequently seen in small herds of two to eight individuals (70. 8 %) . Of the 403 Blue Sheep classified by sex , the ration adult females to males was 1：1. 2 , and the ratio of adult females to young was 1 ：0. 44 ,the population showed a trend of increase. Hunting , human disturbance and livestocks were major threat against Blue Sheep’s lives.