Production of renewable fuels is of growing interest due to the ongoing concerns associated with combustion of fossil fuel contributing to global warming. Biomass-derived bio-oil is a potential alternative replacement for conventional fuels. But negative properties such as lower energy density, higher water content and acidity prevent the direct use of bio-oil as a fuel. It is universally agreed that for production of a viable fuel bio-oils must be significantly upgraded. Present upgrading techniques, such as hydrodeoxygenation and esterification consume high amounts of expensive hydrogen or large volumes of alcohols, respectively. Production of low yields continues to be a challenge for hydrodeoxygenation. Therefore, development of more efficient upgrading methods would be desirable. The current research was divided into two parts: in the first part the raw bio-oil was pretreated prior to upgrading to reduce coke formation and catalyst deactivation during upgrading. In the second part pretreated bio-oils were further upgraded by several techniques. The second chapter describes application of an olefination process to raw bio-oil to produce a boiler fuel. In the third chapter, raw bio-oil was pretreated by novel oxidation pretreatment to convert bio-oil aldehydes to carboxylic acids. Aldehydes lead to coke formation and their conversion to carboxylic acids circumvents this issue. Following oxidation pretreatment to raw bio-oil acid anhydride pretreatment was applied to reduce water content which leads to catalyst deactivation during upgrading. The fourth chapter tests esterification of pretreated bio-oil by oxidation to produce boiler fuel with relatively high HHV. The fifth chapter discusses hydrodeoxygenation of oxidized bio-oil produced by oxidation to increase hydrocarbons yield and reduced charring during hydrodeoxygenation. The sixth chapter describes application of catalytic deoxygenation of pretreated bio-oil by oxidation in the presence of pressurized syngas to produce a liquid hydrocarbon mixture. In the seventh chapter we tested direct hydrocracking of pretreated bi-oil by oxidation to produce a liquid hydrocarbon mixture. The end products were analyzed by following the ASTM methods for HHV, water content, viscosity, density, acid value, elemental analysis. Best performing fuels based on high HHV and low acid value were analyzed by FTIR, GC-MS, DHA, 1HNMR and simulated distillation.