In order to understand the combustion characteristics of the syngas, an experiment was conducted to research the structure, distribution of OH radicals and burning velocity of the syngas-air with OH-PLIF technology. Simulations were also conducted to analyze the chemical kinetics of the combustion process. The results show that the increasing fraction of CO will shrink the structure of the flame, while the height of inner flame varies a little. However, the increasing of H₂ will increase the burning velocity dramatically. The dominant reactions on the formation of OH radical are R36:CO+OH=CO₂+H, R43:H+O₂+M=HO₂+M and R45:H+HO₂=2OH.