The present invention relates to Ag and RE doped nanometer zinc oxide and its preparation process and application in photocatalysis to degrade organic matter and killing bacteria. Ag, RE metals La, Ce, Pr, Nd, Sm, etc. are doped into nanometer zinc oxide to raise its photocatalytic activity in degrading harmful chemical matter and resisting bacteria. Under lighting, the doped nanometer zinc oxide has higher photocatalytic activity and higher antibacterial capacity; and in case of no lighting, it has relatively high antibacterial effect owing to the antibacterial effect one Ag, Zn, RE and other antibacterial ions. The preparation process may be an organic matter complexing process or a sprying pyrolysis process. The doped nanometer zinc oxide may be used through mixing with other material, or used as additive added into plastic, ceramic, fiber, timber, rubber, glass, cement, metal and other material to form various kinds of photocatalytic antibacterial material and product.