Bio-oil is the main product of biomass pyrolysis, which is considered as a promising replacing fuel for fossil oil. But the high oxygen, high viscosity, low heat value and poor stability of bio-oil make it difficult to apply directly. Thus study on the improvement of bio-oil quality is very necessary. Different mass fractions (5%~25%) of methanol, ethanol, octanol and its two mixed alcohols were used to improve the heavy oil quality which was pyrolysed from pine nut. The physical and chemical properties and storage time of heavy oil with alcohol additive were investigated. The results showed that the addition of alcohol additives could significantly reduce the viscosity, water content and pH value of heavy oil, and enhance its heat value. Simultaneously, the contents of phenols, polycyclic aromatic hydrocarbons and ketones in the heavy oil were decreased, and the contents of aliphatic hydrocarbons, aromatic hydrocarbons and alcohols were increased. The heavy oil adding mixed alcohol showed a better stability, and its viscosity and water content were only increased slightly after 56d. After adding methyl-octanol mixture and stored for 56d, the viscosity of the heavy oil was 980mPa·s, and water content was 21.02%. The growth rate was only a half of the original heavy oil. With the increase of methyl-octanol mixture additive amount, the heat value of heavy oil was increased. When the addition amount was 25%, the heat value was 32.66MJ/kg. However, it was found that the combustion performance was the best when adding 20% of methyl-octanol mixture;the weight loss rate of combustion section was the largest and the amount of ash after combustion was minimal.