In this study, a comparative study was made on seed weight and fruiting season in order to improve species of Chinese pepper tree (Zanthoxylum schinifolium S. et Z.) recently used for various purposes and intended to develop a new species. In a test group of Chinese pepper trees, 200 seeds were collected by fruiting seasons and cluster sizes of seeds and their major axis and minor axis and seed weight were measured. Dispersion analysis on difference by cluster size of seeds found that the major and the minor axis and the weight of seeds by cluster had significant differences at 95% of significance level. It was suggested that there were differences in the major and the minor and the weight of a seed by cluster size. It appears that it is more advantageous to develop the species of Chinese pepper tree having smaller cluster of seeds continuously, because a seed of smaller cluster has larger weight. In addition, a dispersion study by precocious, normal, and late ripening species found that there were significant differences in the major and the minor axis and the weight of seeds at 95% of significance level. It found that there were differences in the major and the minor axis and the weight of seeds by precocious, normal, and late ripening species and the weight of a seed and the precocious species had the largest seed weight, so it seems that it is more advantageous to develop the species focused on the precocious species. In conclusion, in order to develop a species of Zanthoxylum schinifolium S. et Z for production of an essential oil, it will be useful to develop species with smaller cluster size and more seeds based on the precocious species.