Ultrafine silver(II) oxide particles-decorated porous ceramic composites have been prepared directly by chemical oxidation, with diatomite-based porous ceramics as the carrier. The prepared composites were characterized by mercury intrusion method, XRD, XPS, FT-IR, SEM, AAS and shake-flask method. The results show that silver(II) oxide decorated diatomite-based porous ceramic composites possess crystal structure and are composed of tetragonal cristobalite, monoclinic silver(II) oxide and cubic silver(I) oxide. The silver(II) oxide weight percentage content of the composites prepared is 8.5% and the average pore diameter, median pore diameter, apparent density and porosity of the composites are 3.862 mu m, 0.354 mu m, 1.794 g mL(-1), and 57.985%, respectively. The composite can release silver in water solution, with a release rate of 7.420 x 10(-3) mg L-1 h(-1). The composites show the strong bactericidal activity. When the contact time with Staphylococcus aureus and Escherichia coli exceeds 20 min, the bactericidal rates reach up to 99.9%. (C) 2011 Elsevier B.V. All rights reserved.