Mannose-binding lectin-associated serine protease 2(MASP-2) is a member of serine protease family and plays a crucial role in activating the complement lectin pathway. When mannose residues on the surface of a pathogen are recognized by mannose-binding lectins (MBL) or fibrinogen collagen (FCN), MASP-2 is activated. This activation then triggers the cleavage of C4 and C2 to form C3 convertase, thereby initiating the lectin pathway of the complement system. Numerous studies have demonstrated that MASP-2 gene polymorphisms and serum levels are closely related with various diseases, including tumors, infectious diseases, autoimmune diseases and so on. In this review, we summarize the relationships between MASP-2 and tumors, infectious diseases, autoimmune diseases. We aim to provide a theoretical basis for the early diagnosis, prognosis evaluation and clinical treatment of various diseases.