The catalytic fast pyrolysis (CFP) of algal biomass was conducted in a newly developed double microfixed-bed reactor. Real-time measurements of catalytic vapors as a function of the cumulative biomass-to-catalyst ratio (BCR) could be achieved by means of a single photoionization mass spectrometer. The coked zeolites were characterized by various methods. During the catalytic conversion of algal biomass, products would tend to be classified into three different types based on their conversion (or formation) efficiency in CFP at the given BCR. More importantly, it was inferred that the "step-1", which had been defined in the CFP of lignocellulosic biomass and would cause the catalyst coking, was lacking in the upgrading processes of algae-based pyrolysis vapors, probably due to the catalytic effect of minerals in algal biomass. This indicates the fact that algal biomass (especially for Sargasso) could be potentially an ideal feedstock to obtain valuable products via CFP. Furthermore, the mass per injection was proven to be an important factor to influence the accessibility of HZSM-5 catalyst due to the "traffic jam" when the primary volatiles enter the zeolite pores.