Abstract: The change of pore water pressure in saturated rocks was closely associated with its damage deformation. In order to study the precursory characteristics of pore water pressure before the damage of saturated rock, the triaxial compression test and seepage test were used in the paper. The research show that:1) During the process of damage in open saturated rock unit, namely phases of the initial compression, elastic compression, plastic deformation and destruction,the pore water pressure would increase, stay stable, gradually decrease, and sharply decrease respectively; 2) Internal damage intensified, cracks connected with the pore water pressure lost steady state could be used as a precursor to rock failure information; 3) The pore water pressure to the development of damage was more sensitive and the response was more obvious in the condition of large pressure change, high pore pressure and high confining pressure; Pore pressure and damage development were interrelated, that the development of damage caused the decrease of pore pressure. At the same time the decrease of pore water pressure promoted the development of damage; 4) It was proposed that internal pore water pressure could be monitored as a method to predict sudden disasters of the rock instability in deep mining engineering.