Abstract: Coal wall instability of large mining height face in steeply dipping is likely to induce the imbalance support-surrounding rock system, leading to the complexity of the stability control of surrounding rock, so the prevention and control of coal wall disaster of large mining height face in steeply dipping is very critical to ensure safe production, the premise of scientific prevention and control technology is to fully understand the instability breeding mechanism of coal wall during the face mining process, so numerical calculations and theoretical analysis are used to carry out the research. The results show that the bearing zones of coal wall of large mining height face in steeply dipping are alienated, the stress concentration in lower part is higher than that in the middle and upper parts, the concentration range decreases from lower to upper, the stress value in the vertical middle of the coal wall is lower, the stress extreme value and strike position are positively correlated with the mining distance, the pressure environment in the neighborhood before and after the coal wall is exposed will change abruptly, and the pressure state will be alienated with the evolution of coal body damage, the bearing structure of the coal body will change from discontinuous state to a quasi-continuous state through compaction, and then move to the threshold as a whole and the fracture occurs, structure discretization. The plastic zone in front of the coal wall expands to different amplitude with the mining action, and its stability is constrained by the mining distance and speed, coal wall stability gradually decreases with the low-speed mining and the increase of the mining distance. The coal body of the plastic fracture development zone is the main bearing body under dynamic and static loads such as abutment pressure, coal wall instability is the dynamic imbalance between abutment pressure and self compressive performance of coal body in disturbance zone, which is broken and unstable due to the qualitative change of coal body structure induced by the quantitative change of pressure bearing behaviors such as migration and deformation, the asymmetry and multi-directional coupling of bearing under the dip angle effect cause the partition and range tendency expansion of coal wall instability.