Abstract: The quality of bio-oil is affected by solid particles. X-Ray Diffraction, Fourier Transform Infrared Spectroscopy and Inductively Coupled Plasma were used to investigate features of the particles. The results show that the content of particles varies with pyrolysis technology, and there are more particles in bio-oil obtained from circulating fluidized bed. The particles mainly consist of char, ash and a small amount of organic polymer. The major components of the ash are metal elements and SiO₂, while of the polymer is oligomer with lignin structure. The content of metal elements is influenced by the characteristics of raw material for pyrolysis.