Abstract: Based on the surveyed data of Helianthemum ordosicum population in different slope positions, the age structure, the static life table, survival curve and mortality curve and vanish rate curve ware analyzed. Additionally, the survival functions were also analyzed. The results indicated that age structure of H. ordosicum in different slope positions exists the trend of decline. The number of young-age individuals accounts a small proportion of total population, that of the middle-age occupies big proportion. The H. ordosicum population density differ in different slope positions, with the characteristics of the biggest population density in upper slope position, less in middle slope position and least in lower slope position. The expectant life span of the first-age H. ordosicum population in different slope positions is maximum, and the fluctuation of expectant life span exists in fifth-age or sixth-age population. The survivorship curves of the H. ordosicum population in different slope positions belong to Deevy Ⅱ～Ⅲ type as a whole. One peak of the mortality rate exists from sixth-age to eighth-age, that on the middle and lower slope position is one age class later than that on the upper slope position. These four function values from the survival analysis could be well used to analyze the structure and dynamic change of H. ordosicum population in different slope positions.

Key words: Helianthemum ordosicum, age structure, life table, survival analysis