In the present study, ceramsite was combined with silver nanoparticles (AgNPs) to fabricate a new nanocomposite for water disinfection. The ceramsite was prepared by fly ash, straw ash, and cement. AgNPs were synthesized using polyvinylpyrrolidone (PVP) as the capping agent. The nanocomposite was prepared by self-aggregation of AgNPs on the surface of the ceramsite. AgNPs capped with PVP can form a thin film on the surface of micropore in ceramsite. The nanocomposite can inhibit bacteria growth and induce damage of the cell membrane of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Therefore, the nanocomposite is a new material which can be used for disinfection in drinking water.