Abstract: The treatment of rare diseases is a global medical problem, and the number of patients with rare diseases has also been increasing year by year. Paroxysmal nocturnal hemoglobinuria (PNH), a rare disease, is targeted at complement component 5 (C5) in all targeted therapeutic drugs, which shows great clinical significance of the target. As one of the important components of complement system, C5 plays a role in innate immunity, participates in immune protection and regulates adaptive immune response. At present, the occurrence and development of many diseases have been confirmed to be related to abnormal activation of C5. Therefore, it has become a hot spot for new drug research and development to study the mechanism of its participation in disease progression and drug development. Nowadays, C5 inhibitors have been marketed. At the same time, C5-targeted drugs like monoclonal antibodies, polypeptides and nucleic acid drugs have entered the clinical trial stage. Therefore, based on the current research on C5 activation mechanism, the research and development progress of C5 inhibitors is reviewed, which provides reference for the research and development and deep application of related drugs.