MCM2 belongs to the microchromosome maintenance [MCM] family and plays an essential role in initiating DNA replication as well as maintaining normal cellular cycle functions. Recent research indicates that there is the abnormal expression of MCM2 in various cancers, such as breast, cervical, ovarian, lung, hepatocellular carcinoma, nephroblastoma, prostate, and pancreatic cancers, where it shows a strong link to tumorigenesis, growth, invasion, migration, and adverse prognosis. Thus, MCM2 could serve as a significant biomarker for the early identification, diagnosis, and prognostic evaluation of multiple cancers. In addition, targeting MCM2 expression may open new possibilities for a full range of cancer treatments. In this paper, the protein structure, physiological function, and carcinogenic mechanism of MCM2 were reviewed.