In recent years, much effort has been directed toward the production of bio-oil from biomass and the upgrading of bio-oil to advanced biofuels. However, most research has focused on promoting the yield and quality of raw bio-oil and exploring valid methods for converting raw bio-oil into hydrocarbons that can be directly processed in a petroleum refinery. In practice, raw bio-oil is unstable and easily changes into viscous compounds with high molecular weights (heavy bio-oil) through polymerization as storage time increases. This leads to added difficulty in subsequent pumping/operating because of the high viscosity of heavy bio-oil (more than 5000 cP at 20 degrees C). Two-stage hydrotreating/cracking experiments were carried out to explore a valid method for improving heavy bio-oil's properties in an autoclave reactor under different process conditions. Heavy bio-oil was placed in an autoclave along with a combination of metal-based catalyst with zeolite. After a heat treatment at 250 degrees C for 4 h, the heavy bio-oil was subsequently treated by quick heating at different temperatures in the range of 300-400 degrees C for about 1 or 2 min. The effects of temperatures and catalysts were examined. The results showed that the properties of upgraded oil, such as water content, density, viscosity, pH, higher heating value, oxygen content, and composition, were modified and lighter upgraded oil with smaller molecules was obtained.