Using the RMT -150B servo - controlling testing machine,a series of triaxial unloading test under high confining pressure condition was made on marble,at the same time,a series of unloading experiments under high confining pressure and hydraulic pressure condition also was done. Based on the experimental results,the unloading deformation,failure and energy properties of marble specimens were studied. The results are as follows: when unloaded at pre - peak,the marble is more brittle than unloaded at post - peak; the high pore water pressure accelerates the brittle fracture of rocks and also reduces their strength; when the marble is unloaded,it is easier to damage under high confining pressure than under low confining pressure.