Abstract: The resource , the population ecology , structure and characters of seeds , pollination biology and the relationship between plumpness of seeds and environment were investigated in the rare plant Changium smyrnioides . The genetic diversity and genetic structure of the species were analysed by morphological characters of seeds , starch gel elect rophoresis and RAPD analysis. The studies revealed lack of coordination between the ripening of the seeds and the season of East China , which resulted in low ratio of seed germination and low rate of population renewal. As human activity has dest royed and disturbed suitable habitat for the species , the range of each population has decreased and the habitat has become f ragmented which has decreased gene flow between populations ( N_m < 1. 0) . The low gene flow suggests that genetic drift may play a prominent role in shaping the present-day genetic composition. Based on these result s , some management st rategies are proposed for protecting this species effectively.