By use of the experiment of bundle tube monitoring on site

the characteristics of fully mechanized sublevel caving mining goaf were analyzed and summarized.Based on the principle of computational fluid dynamics and numerical simulation software FLUENT

the oxygen concentration field

i.e.the key delimiting index of oxidation zone and suffocative zone

was simulated for the different characteristics of fully mechanized sublevel caving mining goaf.The simulation results were compared with experimental results. Considering the different characteristics of goaf

the influence of numerical simulation results on division of"Three Zones"（heat dissipation zone

oxidation zone and suffocative zone）of goaf was discussed. Results show that the characteristics of fully mechanized sublevel caving mining goaf play a very important role in concentration distribution of oxygen and must be considered in the numerical simulation process. Numerical simulation

which ignores the characteristics of goaf

is quite different from experimental results. Whether or not the simulation results are accurate depends on understanding of the problem and setting precision of boundary conditions.