Plant developed safty and efficient xylem vascular system to support long distance water transport so as to provide sufficient water to photothesysis organs. Xylem water transportion play an important role in transpiration, stomental movement, carbon assimilation regulation, therefore be termed “backbone of plant physiology”. Plant hydraulics is the central hub integrating plant and ecosystem function. The present paper summarized the hydraulic mechanism of water transport and the limitation of transport system in plants, highlighted the relationship between the structure and function of xylem vascular. The formation mechanism and induce methods of xylem embolism were described. Tradeoffs between safety and efficiency of water transport system were analyzed. The molecular biology of cavitation and the importance of aquaporin in xylem refilling were discussed. Prediction model as for plant response to environment and drought induced mortality were summarized. The methodological issues were introduced, and the debates on the validity of xylem against pressure refilling and exponential xylem embolization vulnerability curve were discussed. Finally, achievements in xylem hydraulics were summarized, and research chances and prospect were also discussed.