Abstract: Xylem pressure probes are the only technique used currently to measure plant xylem pressure directly.This technique includes devices for accurate positioning, pressure probe systems and signal acquisition.Negative pressure of the xylem vessels is transmitted to the pressure sensor by conduction medium when the capillary probe punctures the xylem vessels, with the pressure then detected and transmitted to the data acquisition system.In this paper, the use and precautions of xylem pressure probes are described in detail, including the preparation of glass capillary probes, degassed water, pressure calibration, installation, and measurement of pressure probes.