The difference between ornidazole and metronidazole mainly lies in the effect of action, adverse reactions and drug metabolism. 1. Effect: metronidazole and ornidazole both belong to nitroimidazole drugs, both are mainly for anaerobic bacteria and trichomonas-related infectious diseases, but ornidazole is stronger than metronidazole on anaerobic bacteria. 2. Adverse reactions: the side effects caused by ornidazole are relatively small, metronidazole often causes stomach pain, nausea, vomiting and other gastrointestinal reactions, while ornidazole causes related adverse reactions are relatively small. 3. Drug metabolism: the plasma elimination half-life of oral ornidazole is about 14 hours, while the half-life of metronidazole is relatively longer, which means that metronidazole metabolism in the body needs a longer time. The above drugs need to be used under the guidance of a doctor, the specific use of which drugs, need to be chosen by the doctor, in order to better treat the disease.