Abstract: Using filtration-burning method to measure the solid matter content in FCC heavy oil, the particle size distribution, chemical composition and structure of the solid matter in slurry oil, recycle oil and VGO were analyzed in detail. Results showed that the main solid matter in slurry oil was catalyst, which particle size was in the range of 0.5—20.0 μm. The compositions of solid matter in recycle oil and VGO were complicated, besides catalyst particle, also some Fe2O3 and Sb2O5. It seemed that Fe2O3 was from the corrosion of equipment and pipeline, Sb2O5 might come from passivating agent used in FCC process, their particle size distributions were rather wide with quite an amount of particles over 100 μm.