Abstract: Load/unload response ratio(LURR) theory is a representative method for studying stability of nonlinear system.Through three types of load/unload paths，LURR of three typical types of rocks are analyzed，including sandstone，marble and serpentinite sampled from Dongguashan copper mine.With the axial stress as input parameters，LURR of axial strain shows little change with load increase under uniaxial compression，whereas，presents sharp increase and drops when close to the peak.LURR of circumferential strain appears abnormal increase during the medium-term load.Under the three axial compression，the confining pressure keeps constant，and the LURR of axial strain and circumferential strain of axial load-unload is similar with that of the uniaxial compression.The definition of simple loading and unloading of confining pressure with constant axial compression is studied，and the LURR of axial strain and circumferential strain showed stable and then sharply increased when close to failure during the process of loading and unloading confining pressure step by step.Finally，the failure characteristics of rock under different stress paths were analyzed.

Key words: Brittle rocks, Load/unload response ratio (LURR) , Stress path