Abstract: The mesoporous silica-P123 composites were prepared by the sol-gel method using three block copolymer polyoxyethylene-polyoxypropylene-polyoxyethylene (PEO-PPO-PEO, P123) as template agent. The composites were calcined to remove P123 and the rod-like mesoporous silica particles with different aspect ratios were obtained. The mesoporous silica particles were dispersed in polyethylene glycol (PEG) to form shear thickening fluids (STF), whose rheological properties were characterized by rotary rheometer. Results indicated that under steady shear, shear thickening effect increased as the mass fraction of the mesoporous silica increased, while decreased as the aspect ratio of the mesoporous silica increased. Under dynamic oscillation, shear thickening effect decreased as the mass fraction of the mesoporous silica increased, while increased as the aspect ratio of the mesoporous silica increased.