Abstract: The lateral wall stability of underground mining in a copper mine in Jiangxi province was analyzed in theory.Firstly，the stability analysis model of movable blocks under crustal stress was proposed，then based on the principle of force balance，the relationship formula between the principal stress and the direction and angle of rock mass structural plane was established，and the sliding resistance equation of movable blocks was obtained.Based on this，the stability coefficient equation of blocks along the double sliding was established.The calculation results showed that the stability value of block decreases with the increasing of angle between maximum horizontal stress direction and stoping drift direction；When the maximum horizontal stress direction is the same as stoping approach direction，the stability value of block increases.The effect of the maximum horizontal stress on the stability of the block is in connection with the principal stress value and the occurrence of rock mass structural plane.

Key words: Lateral wall, Movable block, Crustal stress, Stability coefficient