NOVELTY - Method of improving efficiency of catalytic pyrolysis of a biomass feedstream involves determining the processability index (PI) of lignin-containing biomass feedstream, subjecting the biomass feedstream having PI value of more than 15 to physical processing for predetermined time to lower the PI value, introducing the treated biomass into a biomass conversion reactor, and subjecting the treated biomass to catalytic pyrolysis.    USE - Method of improving efficiency of catalytic pyrolysis of biomass feedstream used for producing renewable fuel sources.    ADVANTAGE - The method is environmentally-friendly, and enables efficient and economical improvement of catalytic pyrolysis of biomass with high quality and high productivity.    DETAILED DESCRIPTION - Method of improving efficiency of catalytic pyrolysis of a biomass feedstream involves determining the processability index (PI) of lignin-containing biomass feedstream, subjecting the biomass feedstream having PI value of more than 15 to physical processing for predetermined time to lower the PI value, introducing the treated biomass into a biomass conversion reactor, and subjecting the treated biomass to catalytic pyrolysis. The processability index is calculated using relation of formula: PI=100x ((S/G)x (%acetate)x (Alkaline+Non-metal+Metalloids)2)/((%xylan)x (Alkaline Earth)) where, S/G is the ratio between S-units population and G-unit population in the lignin component of the biomass feedstream, %acetate is the content (in wt.%) of acetate in the biomass feedstream, Alkaline is the total amount (in wt.%) of group I metals in the biomass feedstream, Non-metal is the amount (in wt.%) of element of group 15, group 16 and group 17 in the biomass feedstream, Metalloids is the amount (in wt.%) of group 13 and group 14 elements in the biomass feedstream, %xylan is the content (in wt.%) of xylan component in the biomass feedstream, and Alkaline earth is the total amount (in wt.%) of group II metals in the biomass feedstream.