Abstract: With the development of social economy，the production of all kinds of garbage is increasing rapidly， and the research on efficient and clean utilization of pyrolysis gas of garbage is gradually carried out． This study used FLUENT software to simulate the MILD combustion of MSW pyrolysis gas in the burner，and the effects of fuel nozzle diameter，air nozzle diameter，distance between fuel nozzle and air nozzle，air nozzle distribution and thermal value fluctuation on the combustion and NO emission in the burner were explored． The results show that the change of jet velocity indicated by the change of air nozzle diameter has the most significant effect on combustion， and the increase of jet velocity can achieve better MILD combustion effect by turbulence and entrainment． And there is an optimal value of 8mm of air nozzle diameter in this study． The increase of fuel jet velocity has less effect on combustion effect，the high speed of fuel jet is conducive to fuel jet rigidity and combustion zone extension，and there is an optimal value of 8 mm of fuel nozzle diameter in this study． The diffusion process and the size of return area can be influenced by the distance between air and fuel nozzle，which can be matched with the aperture to obtain an optimal value when the nozzle spacing is 15mm． The uniformity of the air jet distribution affects the combustion effect，but has little effect on NO emission，so 4 air nozzles are suitable． The burner can satisfy the MILD combustion with the calorific value of the pyrolysis gas fluctuating at 20% ．

Key words: pyrolysis gas, MILD combustion, numerical simulation, structural parameters, jet velocity