In this study catalytic and non-catalytic co-pyrolysis of pretreated and intact sugarcane bagasses using waste heavy paraffin (as an in-situ supply of hydrogen) were investigated. The catalyst examined in this study was a commercial zeolite catalyst (HGY-A), which is a gasoline boosting catalyst, suitable for cracking hydrotreated residues in oil refining industries. Co-feeding of bagasse with paraffin produced higher liquid product yields and lower solid yields. The improved effective hydrogen to carbon ratio (H/C eff ) of the feedstock, and primary cracking and fragmentation reactions of heavy paraffin at temperatures around 600 o C are responsible for considerable improvement of bio-oil yield. Use of HGY-A catalyst did change the compositions organization of the produced bio-oil; however, it did not have any impact on the bio-oil yield under various operational conditions. Results showed that acidic pretreatment (with 30% W/W HCl) lead to decrease of bio-oil yield by 11 %w and increased the char yield by 9 %w. In addition, since cellulose is a dominant component in lignocellulosic compounds such as bagasse, this material was used as a model compound to examine the mechanism of conversion process to products. Cellulose as bagasse and other biomasses has a hydrogen deficiency and for compensation of this lack of hydrogen heavy paraffin with a ratio of cellulose:heavy paraffin (85:15 w:w) was added and pyrolysis was done at 600 ?C. Bulk yields and chemical components of the products were obtained for the pyrolysis of the feeds alone and in the mixture. It was seen that the bio-oil was the major product for pyrolysis and co-pyrolysis processes and its concentration slightly increased from 52.45 % w to 55.98 % w with the addition of paraffin. The bio-oil properties were obtained by FTIR and GC-MASS apparatus. As FTIR results bio-oil obtained by the paraffin pyrolysis is reach in aromatic and aliphatic hydrocarbons but the bio-oil from the pyrolysis of cellulose is a miscellaneous mixture of oxygenated compounds and aromatic and aliphatic hydrocarbons. These findings are verified with GC-MASS results. Moreover, the components identified by GC-MASS apparatus were grouped into 10 pseudo-components for easier comparison and the main subunits of each group were determined and the chemical reaction pathway for their production was mentioned. Paraffin addition to cellulose led to an increase in hydrogenolysis, hydrogenation, condensation and transglycosylation reactions. Moreover, furan ring opening increased which led to the higher production of aldehydes (5.48 %w vs 0.37 %w for bio-oil from cellulose). Diels-Alder reaction caused to the more production of aromatic hydrocarbons (8.31 %w vs 6.27 %w for bio-oil from cellulose). Also, more aliphatic hydrocarbons were obtained by capping of free radicals at the presence of hydrogen and hydrocarbon free radicals of paraffin. Further Fischer Esterification reactions are diminished and as a consequence, the alcohols production increased. In addition, similar to cellulose, in order to determine the effect of acidic pretreatment of bagasse, paraffin addition to bagasse and HGY-A zeolite catalyst addition to the mixture of bagasse and paraffin on the bio-oil chemical components distribution, the liquid produced from the pyrolysis, co-pyrolysis and catalytic co-pyrolysis was analyzed by GC-MASS apparatus. As mentioned previously the chemical components are grouped into ten pseudo-components and the main subsets of each group identified and the chemical reaction pathway for their production is mentioned. With bagasse pretreatment dehydration, hemolysis of methoxy groups, alkylation reaction and demethylation increases but esterification reactions is limited. Paraffin addition to bagasse caused to an increase in hydrogenolysis and condensation reactions. Further, transglycosylation and furans ring opening grow in presence of paraffin free radicals. With catalyst addition, increase in phenolic (by 5.14 %w) and furan (by 6.31 %w) compounds observed. De-esterification, isomerization, hydrogenolysis and dehydration are the other main reactions in presence of catalyst. Also, cyclopentenone production accelerates by rearrangement and isomerization reactions of furan compounds.