Abstract: The mechanical parameters of coal rock were measured through unconfined compression experiment，then the mesomechanical parameters of coal rock were obtained by particle flow code and Fish program and experiments were carried out under unequal bilateral confining pressure． It was analyzed the mechanical and deformation property and acoustic emission characteristics in the failure process of coal rock． Some main research results were as follows: with the increasing of confining pressure ratio，coal rock stiffness angle increased，slightly，brittleness angle increased， strengthening angle kept constant，softening angle first increased and then decreased; Confining pressure ratio had no effect on volumetric strain in linear compression stage，obvious effect on the linear expansion stage and significant effect on the nonlinear expansion stage． In nonlinear expansion stage，coal rock volumetric strain still was linear on lower confining pressure ratio while coal rock rapidly expanded and instability on higher confining pressure ratio． The maximum intensity of acoustic emission lagged behind the peak stress，confining pressure ratio had no effect on the lag， the ratio of stress at acoustic emission maximum strength to peak stress was about 0. 92; On lower confining pressure ratio，shear failare occured along a single shear surface of coal rock，on higher confining pressure ratio X conjugate shear failure occured． Main failure surface width increased and developed into fracture zone with the increasing of confining pressure ratio，the coal rock in the zone was a crushing failure state．