Abstract: Studies on the fine stereo-structure and biological activity(PAF antagonisticaction)of lignans from Piper kadsura were carried out by chcosing three structural types for X-raydiffraction single crystal structural analysis to get the stereo-structure parameters.Molecular graphicsand molecular mechanics were used to get stereastructure data of nine molecules from the threestructural types under free state。Structure and activity(PAF inhibition)analysis was based on knowndata² from pharmacedynamic experiment.