Abstract: The three-dimensional distribution of the velocity value of isothermal flow in high temperature air combustion furnace was numerically simulated with a computer program. Three types of isothermal flow configuration were forecasted under the conditions of three different velocity ratios of fuel to air inject. The flow field properties of the interaction among multi-injections and the recirculating flow were analyzed. It was shown that under certain geometrical parameters, the lower oxygen concentration in recirculating flow can be obtained in the furnace by selecting proper velocity ratio of fuel to air jet in same scalar level. The simulating conclusions are in agreement with the experimental results.