The invention provides a nanometer montmorillonite sustained release agent of an azomycin medicament The sustained release agent is prepared by inserting 10 to 45 weight portions of the azomycin medicament into the interlayer of 100 weight portions of Na-montmorillonite in a protonizing way under the condition of the pH value of 1.0 to 5.0 by adopting a liquor intercalation method; the azomycin medicament is metronidazole or tinidazole; the Na-montmorillonite is obtained by using Na<+> to replace Ca<2+> and Mg<+2> in the material of montmorillonite. The sustained release agent takes the montmorillonite as the vector of the azomycin medicament, which not only has the effects of releasing the medicament and improving the targeting, but also combines the characteristic that the montmorillonite can absorb pathogens and toxins, and can greatly improve the concentration of the partial medicament in a body, thereby reducing the medication times and species of the medicament.