Abstract: In order to provide basic data for utilizing bio-oil, flash pyrolysis of pulverized corn stalk was conducted in a plasma heated fluidized bed reactor. The yield of bio-oil derived from corn stalk by pyrolysis is about 37%. The physical and chemical characteristics of the bio-oil were then determined. Bio-oil is acidic (pH ranges between 3.8～4.0) with density of 1100～1200 kg/m³. The kinetic viscosity of bio-oil decreases quickly with the increase of temperature up to 27.5℃, and then decreases slowly. The ash content of bio-oil is less than 0.1%. The chemical compositions of the bio-oil were analyzed by gas chromatography-mass spectrometry (GC-MC). The major chemical compositions detected were acetic acid, 2-propanone, 1-hydroxy, water, acetaldehyde, hydroxy, furfural, etc. Because of high content of oxygen and water, the heat value is relatively low and polymerization may react easily. The bio-oil derived from corn stalk must be analyzed further and upgraded before its application in advanced areas.