Taking the physical model of downdraft biomass gasifier as the research object, fluid simulation software Fluent was used, the pressure field of the gasifier that in the condition of single-layer air-distribution and double-layer air-distribution was comparatively analyzed. By means of multi-point pressure measurement experiment, the simulation results were verified. The Euler-Lagrange model was used to analyze the cold characteristics flow field distribution of gasification. The reason of diversification in pressure field by Bernoulli’s equation was discussed. The results showed that the deviation value of simulation and experimental results was under 2.5%. Different air-distribution condition should lead to the changes of flow field in biomass gasifier. Double-layer air-distribution condition made the average pressure in oxidation area of 14.98kPa, higher than that in the condition of single air-distribution. And also the axial direction pressure distributed equally. 