Abstract: With the aim of studying chemical compounds and application of complicated bio-oil pyrolysed from corn stalk, bio-oil was analyzed using gas chromatography/mass spectrometry (GC/MS), and the physical characteristics of emulsified fuel (EF) made by water-soluble bio-oil and diesel oil were determined. Bio-oil was comprised of two fractions: water-soluble and water-insoluble fractions. The major chemical compounds in water-soluble bio-oil occupied 80% of the total weight were water, acetic acid, 2-propanone-1-hydroxy, cyclopentenone, furfural and phenol, etc. After water-soluble bio-oil was extracted by dichloromethane (CH2Cl2), some compounds were detected, such as the derivatives of cyclopentenone, furfural and phenol. Water-insoluble fraction was so complicated that it was difficult to confirm compositions directly. Experiments were also conducted to study the stabilization of EF made by water-soluble bio-oil, diesel oil and emulsifier which was made by Span-80 and Tween-20 according to a certain proportion, and it was concluded that long reaction time, higher concentration of diesel oil and emulsifier or lower concentration of water-soluble bio-oil could lead to good stability. The heat value of EF was much higher than that of water-soluble bio-oil, but the pH value of EF did not change much better than that of water-soluble bio-oil. Some methods must be taken to reduce acidity of EF in order to apply in diesel engine.