The effect of particle size of silica, as catalyst binder, on the chemical and mechanical properties of iron based FT catalyst was studied in this work. The samples were characterized using XRD, BET, TEM, FT-IR, and H2-TPR, respectively. The attrition resistance and the FT activity were tested. Si-8-Si-15 catalysts prepared with 8-15 nm silica sol show good attrition resistance (attrition loss < 4%), especially Si-13 with an attrition loss of 1.89%. Hematite appeared in XRD patterns when silica sol above 15 nm is used. TEM micrographs show that no obvious SiO2 particles appear when silica sol particle with size less than 8 nm was used, but SiO2 particles coated with small ferrihydrite particles appear when silica sol above 8 nm was used. Si-O-Si vibration peak in FT-IR spectra increases with increasing silica sol size. Samples prepared with silica sol show good stability of FT reactions, and the average molecular weight of FT products increases with the increase of SiO2 particle. (C) 2016 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.