P27 is a kind of cyclin-dependent kinase inhibitor(CKI). Its regulation function during cell cycle and many other biological features have been found , causing the widespread attention of people. In addition, as an anti-oncogene , p27 is an independent prognostic factor in many human tumors and can be the marker of clinical diagnosis. Advanced research of p27 is a very important job for recovering the mechanism of life course and preventing tumors.