Abstract: By use of segregation process, a research of Pericarpium Zanthoxyli is made into issues like the molecular type of its secondary xylem vessel, the length of the vessel elements, the caliber, the type of perforated plate and aft-end features. The results show that the molecular wall of the vessel is characteristic of a pitted vessel; the end part of the vessel elements has no end; cases of single end or two ends are both observed; the vessel molecular perforated plate is principally a simple perforation plate, which is located either in the end wall or in the side wall; of which some even form a twin opposite pit in the side wall. This clearly indicates that Pericarpium Zanthoxyli is a rather developed plant, although the developmental degree varies in different vessel molecules of the species or in the different traits of the same vessel molecule; the development of the secondary xylem vessel plays a role of the system development in the cultivation of Pericarpium Zanthoxyli.