Abstract: Choosing the Myristicaceae yunnanensis populations in tropical rain forest of Xishuangbanna as the study target,the age structure and spatial structure were investigated through sampling plot method.It was found that Myristicaceae yunnanensis populations showed the tendency of decline.As far as the spatial distribution characteristics was concerned,and by use of the methods such as minimum distance,spatial distribution index,negative binomial parameter,clumping index,average crowded degree or index of patchiness,all the results indicated that Myristicaceae yunnanensis populations displayed the aggregated distribution pattern.Time-specific life table,survival curve,equation of linear regression and significance test all exhibited the characteristics of population decline.The equation regression was linear type.