Rock is a kind of physical nonlinear complicated medium, under deepburied condition the surrounding rock system deformation shows geometrical nonlinear characteristic, and the interaction between the two nonlinear mechanism makes the unloading of surrounding rock system evolving complexly. Based on the Lagrangian method and large deformation caculation method, both the doublenonlinearity and nonlinear dynamics character of deepburied tunnel surrounding rock system under unloading are studied. The numerical model results show that the Kolmogorov entropy has been extracted from the evolution data in the unloading process of surrounding rock system. The analysis indicates that the typical chaos character has been demonstrated in the process of unloading for deepburied tunnel surrounding system and the rock mass energy dissipation is analyzed at the stage of unloading.