A cold model (its ratio is 1:12.5) of a 50 MW tangentially pulverized coal-fired boiler was built and the mixture characteristic between a simulating gas (hot air) and a main airflow (cold air) were gotten at different ejecting methods and quantities of the simulating gas through measuring the temperature pattern distributing in the furnace of the model. The simulating gas spouted from front and rear walls resulted a more even mixture characteristic, and the tangentially ejected simulating gas is more suitable for the tangentially pulverized coal-fired boiler, and the tangentially ejected OFA is also of advantage to it. The effect of quantities and locations of the simulating gas on the mixture characteristic was also discussed.