Abstract: 【Objective】 To study the effects of spatial distribution and reproductive traits on the fitness of S. chamaejasme populations,and to explore the relationship between S. chamaejasme populations and environment at different successional stages.【Method】 The spatial distribution characteristics of the S.chamaejasme population were studied using RTK（i. e., Real-time kinematic） technology; the individuals were divided into three classes according to the number of inflorescences as follows: class Ⅰ（1～10branches）,class Ⅱ（11～20 branches）,and class Ⅲ（more than 21 branches）. Then,the age structure of the population and the relationship between the reproductive fitness with population density and phenotypic characteristics of individuals were analyzed.【Result】 Class Ⅰ seedlings accounted for 79% of the individuals tested,class Ⅱ seedlings for 14. 4%,and class Ⅲ seedlings for 6. 6%. The distribution of individuals in different branches showed an inverted "J" curve,and the survival curve was Deevey Ⅱ,reflecting an age structure of the growth stage of the population. Overall,the spatial distribution pattern of the population was characterized by cluster distribution,with slight differences among the three grades of individuals. The individuals for classes Ⅰ and Ⅱ were obviously aggregated,while the adult plants tended to be randomly distributed. Individual reproductive fitness was significantly positively correlated with plant density（R~2=0. 096,P=0. 017）,inflorescence density（R~2=0. 104,P=0. 010）,and the number of flowers per inflorescence（R~2=0. 172,P=0. 001）. There was a negative correlation between the fitness and plant size（i. e.,inflorescence number）（R~2=0. 077,P=0. 034）,but not significant with plant height.【Conclusion】 The S. chamaejasme population was characterized by the age structure of growth type and by spatial pattern of aggregation distribution,with significant effects of population density,plant size（i. e.,inflorescence number） and number of flowers per inflorescence on the fitness and no effect of plant height.