Ultra-pure mesoporous silica microspheres with good monodispersity were synthesized in two steps:nanometer-sized silica sol was produced by the sol-gel process,then micrometer-sized silica microspheres were synthesized by polymerization-induced colloid aggregation of the silica sol.The total metal content of the microspheres was extremely low,which eliminated the tailing of chromatographic peaks by chelating reagents.The pore structure of the silica microspheres could be controlled by altering the sol-gel conditions.The silica microsphere particle size could be adjusted by using different polymerizationinduced colloid aggregation conditions. Ultra-pure mesoporous silica microspheres with good monodispersity were synthesized in two steps: nanometer-sized silica sol was produced by the sol-gel process, then micrometer-sized silica microspheres were synthesized by polymerization-induced colloid aggregation of the silica sol. metal content of the microspheres was extremely low, which eliminated the tailing of chromatographic peaks by chelating reagents. The pore structure of the silica microspheres could be controlled by altering the sol-gel conditions. The silica microsphere particle size could be adjusted by using different polymerizationinduced colloid aggregation conditions.