The circulating fluidized bed gasifier (CFBG) has become an important and promising technology in biomass conversion. In this paper, a series of investigations were conducted with a biomass CFBG in order to demonstrate its performance. The CFBG was operated at atmospheric pressure with gum wood powders. The experimental results indicate that the CFBG can operate over a broad range of operating conditions with satisfactory gasification results. Based on the discussion of gasification processes, it was found that fast pyrolysis of biomass is the most important process which makes the CFBG so advantageous. Analysis of the experimental data highlights the important roles of temperature and secondary reactions so suggesting favourable operation conditions.