Abstract: In order to improve water quality through filtering microbial and impurities in water, Ag doped hydroxyapatite (Ag-HA) antibacterial powders were prepared by one-step-coprecipitation method, and they were mixed with raw materials such as diatomite and kaolin etc. to prepare Ag-HA/diatomite-kaolin composite ceramics by sintering method firstly. Then, the structures of Ag-HA/diatomite-kaolin composite ceramics were characterized by XRD, SEM, EDS and atomic absorption spectrophotometer. Finally, the antibacterial properties of Ag-HA/diatomite-kaolin composite ceramics for Escherichia coli (E.coli) and Staphylococcus aureus (S.aureus) were investigated. The results show that the main phases of Ag-HA/diatomite-kaolin composite ceramics are quartz, cristobalite and HA. Ag-HA/diatomite-kaolin composite ceramics contain numerous channels after high-heat sintering, which are made up of the micron scale pores between diatomite particles and the pores in particles; microcrystalline Ag distributes uniformly in Ag-HA/diatomite-kaolin composite ceramics. When Ag content is 0.098wt%, the minimal inhibitory concentrations against E.coli and S.aureus are 100 μg/mL and 50 μg/mL respectively. Bactericidal rates of block or powdery Ag-HA/diatomite-kaolin composite ceramics against E.coli and S.aureus are 60.76% and 100.00% within 1 h, both reach 100.00% after 3 h, and possess persistent antibacterial properties within 24 h. The conclusions obtained indicate that the prepared Ag-HA/diatomite-kaolin composite ceramics are a promising filter for water treatment.