The three-dimensional numerical simulation of the non-premixed combustion turbulent mixing processing in high temperature combustion furnace have been performed with authors developed computer program of flow,combustion,heat transfer and NO_x turbulent formation.The 3d-distributions of mixture fraction and its turbulent fluctuation are forecasteed under three different inlet air temperature conditions in combustion furnace.Compared with non-premixed combustion,the results demonstrate that,under certain geometry and dynamical conditions,the turbulent mixing of high temperature air combustion proceeds with smaller intensity within a larger zone; the turbulent mixture fluctuation distributes within the larger combustion zone.This also indicates that the flame thickness appears to be larger and that heat is released within larger combustion zone.The simulating conclusions are in agreement with the results of similar experiments.