Abstract: Hemicellulose can produce more acid content than cellulose and lignin via pyrolysis. This work reduced the hemicellulose and water content of pine via low temperature pretreatment to improve the bio-oil quality. The chemical composition and FT-IR analysis of pine after pretreatment show that the lignin content increases and the carbonization of pine takes place, which results in the decrease of bio-oil yield and the increase in yield of char and no-condensed gas. With increasing pretreatment temperature, the important characteristics of the bio-oil, such as water content, high heating value, kinematic viscosity, and density all increase, and solid particles content decreases, while pH value decreases after an initial increase. The ¹³C nuclear magnetic resonance (NMR) show that the aliphatic carbon of bio-oil decreases, while the aromatic and the aromaticity increases.