Abstract: A Micro Fluidized Bed Reaction Analyzer (MFBRA) was used to study the pyrolysis of biomass in argon. Through on-line pulse feeding of reactant and continuously monitoring the composition changes of gas product, the MFBRA enables the measurement of reaction rates at arbitrary temperatures, the deduction of kinetic parameters and the analysis of reaction mechanism. By applying to biomass pyrolysis this article found that the pyrolysis reaction can finish in about 10s, which is much shorter than the other literature values obtained in larger fluidized bed reactors but very close to the theoretically anticipated values. The detected evolving sequences of different gas species and the deduced kinetic parameters demonstrate further that the reactions between/among the formed different gas species in pyrolysis prevail to certain degree and there are different pathways for forming the different gas species. The activation energy and pre-exponential factor derived by treating the pyrolysis gas as a single product are 11.77kJ/mol and 1.45s^-1, which are obviously lower than the literature values measured in thermogravimetric analyzers.