Corn straw was pyrolyzed in a bench-scale fluidized bed reactor. In the experiments, the influence of pyrolysis temperature, biomass particle size, and vapors residence time on the product distribution was investigated. In addition, optimization of the key parameters for corn straw fast pyrolysis for bio-oil production was conducted according to orthogonal experiment design. Results showed that pyrolysis temperature and vapors residence time had an obvious effect on bio-oil yield, while their interaction and biomass particle size had unnoticeable effect on it. The maximum bio-oil yield was 42.00 wt% at the optimal condition (pyrolysis temperature 525 degrees C, biomass particle size <0.45 mm, vapors residence time 0.8 s). Analysis of bio-oil with GC-MS showed that bio-oil was the mixture of complex organic compounds with the extensive existence of oxygen. The research has provided a reference for biomass fast pyrolysis.