Beta B₂-crystallin is the most abundant crystallin in the β-family, which plays an important role in the maintenance of the lens transparency and refraction. The abnormal of beta B₂-crystallin may be associated with the formation of various types of cataract. In recent years, the mechanism of cataract which caused by the related mutations of CRYBB₂ gene is becoming a hot spot of research. This article summarized the structure, function and mutation of beta B₂-crystallin and its relations with various types of cataract.