Abstract: In order to investigate the effects factors on the bio-oil yield,orthogonal experiments on the pyrolysis of corn stalk in a fludized bed reactor heated by Ar plasma which was made in Shandong University of Technology were carried out. With the input power, Ar flow rare, reactor pressure and feeding rate as input factors, the bio-oil yield as the output,the square combination experiments of four factors and five levels with orthogonal rotation were conducted. The results showed that when the input power was 38.5 kW, Ar flow rate was 2.0 m3/h, pressure was 200 mm water column, feeding rate was 0.87 kg/h, the highest bio-oil yield was 58.45%. The pressure in the reactor and feeding rate were the main factors to the bio-oil yields, while the input power and Ar flow rate were the second factors.