Rare-earth doped fibers are the foundation of fiber lasers while the photodarkening of doped fibers is a significant factor which is harmful to the stability of laser output power. In this paper, we review the mechanics of photodarkening, and the influence of photodarkening on the fiber lasers, as well as all kinds of methods which can mitigate the photodarkening effects in the doped fiber, with the aim of providing useful information for the related research.