Aiming at the disadvantage that nano ZnO is easy to agglutinate in the process of preparation and use， which will affect its antibacterial performance， experiments are designed to make nano ZnO compound with porous SiO₂ in the sol-gel process. Through scanning electron microscope （SEM） and transmission electron microscopy （TEM）， it can be found that ZnO is well combined on the porous SiO₂ skeleton and dispersed evenly. The BET and PL tests show that the specific surface area of composites is improved and the optical properties are enhanced. The difference of antibacterial properties between composites and single-component nano ZnO， and the change of antibacterial properties caused by the change of nano ZnO content in composites are investigated by the colony counting method. Conclusion is proved that the antibacterial properties of nano ZnO and porous SiO₂ are greatly improved with the antibacterial rate of more than 99%.