Abstract: The temperature control of the flame zone plays an important role for synthesis gas preparation by the co-gasification of natural gas & coal. In this paper the factors affecting the temperature of the flame zone were investigated using a laboratory scale fixed bed reactor to simulate the industrial furnace for synthesis gas preparation. The inlet positions of methane and oxygen that make the flame minimum temperature were first investigated. Then the effects of the ratio of H2O/O2 and CH4/O2 in feedstock on the flame temperature were studied respectively. The experimental results show that the flame temperature is the lowest when the inlet position of CH4 and O2 is at the same level. Under this condition, the flame temperature decreases when the ratio of CH4/O2 and/or H2O/O2 is increased.