The long-time running of a high power Yb-doped fiber laser will cause photodarkening, which reduces the output power of laser. Thus, the research on photodarkening in Yb-doped fiber is of great significance to the development of Yb-doped fiber laser. The latest progress of photodarkening in Yb-doped fiber is detailedly introduced in three aspects including mechanism, impact and suppression method, which provides reference for the further study of the photodarkening.