The pyrolysis of biomass micron fuel (BMF) with particle size of less than 250 mu m was carried out in a lab-scale free-fall reactor. The influence of pyrolysis temperature, particle size, and feed velocity on the product distribution was investigated. In addition, The optimum pyrolysis parameters of bio-oil production from BMF pyrolysis were determined via orthogonal experiments. The experimental results showed that in the range of experimental parameters, the order of the effects of the factors on bio-oil yield of BMF pyrolysis is pyrolysis temperature > particle size > feed velocity. Pyrolysis temperature and particle size had a significant effect on bio-oil yield. The maximum bio-oil yield was 41.05 wt.% under the optimal conditions (pyrolysis temperature 500 degrees C, particle size <91 mu m, feed velocity 12.5 g/min). The gas chromatography-mass spectroscopy (GC-MS) analysis of bio-oil obtained in optimum pyrolysis conditions indicated that it was the mixture of complex organic compounds with high oxygen content. The present study provides useful reference data for BMF pyrolysis. (C) 2012 Elsevier Ltd. All rights reserved.