Human microcephalin 1（MCPH1），also known as BRCT-repeat inhibitor of hTERT expression（BRIT1），is a chromatin-binding DNA damage response protein containing 835 amino acids with 110 kD molecular weight. It interacts directly with a variety of important proteins including cancer-related gene proteins（E2F，p53，BRCA1/2，etc），DNA damage response proteins（ATM，ATR，RAD51 and Condensin Ⅱ，etc） and cell-cycle regulators（CDK1，cyclins）. MCPH1 is likely to play an important role in the main－tenance of genomic stability through its activities in cell-cycle progression，DNA damage repair，and tumor suppressor. In this review，we summarized the biochemistry structure of MCPH1 and its role in maintaining the genomic stability and described the relationship of MCPH1 deficiency with human cancer development.