Abstract: Bio-oil produced by medium temperature fast pyrolysis has disadvantages of high acid, high oxygen content and low heating value and can be used as fuel after some modification process. In terms of Hydrophilic-Lipophilic Balance (HLB) principle, bio-oil was emulsified with number zero diesel fuel to reduce the acid value and improve its performance. SEM, EDS and other analytical techniques were used to analyze the corroded metal surface after four general metals (pure copper, stainless steel, aluminum alloy and lead) were corroded at 25℃ and 50 ℃ respectively. The results showed that the corrosion degree of metals caused by emulsification biological oil was in sequence of aluminum alloy> lead> pure copper> stainless steel. Moreover, the higher temperature, the more serious corrosion to metals. The corrosion mechanism was ascribed to generate the metal oxide on the metal surfaces.