Abstract: In this paper, aiming at the existing defects of rock burst study, a splitting catastrophe model of unloading rock burst of surrounding rock was established based on the mutation theory, and the necessary and sufficient conditions of splitting rock burst were obtained while considering the unloading influence, then the sensitivity of influence factors was further analyzed. The results show that the mutation characteristic value and critical condition of rock burst were reduced obviously by excavation unloading, and the occurrence possibility of rock burst increases greatly，when the tensile stress meets the condition of σx=πσt/4, the necessary conditions will become the sufficient conditions. Meanwhile, the surrounding rock will be displaced after a period of unloading, the standard or delayed rock burst will occur when the unloading microscopic tensile stress reaches the needed condition to induce rock burst, while the instant rock burst occur will occur when the vertical stress reaches to a certain value and the mutation characteristic value of surrounding rock during unloading moment meets the condition ofΔ≤0. In addition, the splitting of rock burst should satisfy a certain size requirement of free surface, and the requirement can be reduced significantly with the increasing of vertical stress. Moreover, the vertical stress have important influence on the ΔE，σx and Δ, while the horizontal stress have more im-portant influence on the Δ.

Key words: hard rock, unloading rockburst, splitting criterion, mutation, sensibility