AbstractThe effects of population density of Mosla hangchowensis was studied. The results showed : (1) In the growing season , its mortality rate depended on its population density of M. hangchowensis. The optimal density of M. hangchowensis was 200～1000 individuals/ m2 . (2) The relationships of the plant height or number of flowers bloomed and the dates fitted the Logistic function. (3) In the growing season ,about 60 % of individuals at a high density can complete their life cycle , whereas , 85 % at a low density can do. Most of morphological and reproductive traits were density dependent .