Abstract: In this review, we described the studies of two types of gene duplication (large-scale, small-scale gene duplication) and three alternative ways of divergence (neofunctionalization, subfunctionalization, pseudogenization) with protists in detail. Moreover, we introduced the studies of retention bias of duplicated gene and three evolutionary models within protists briefly. It is suggested that more researches should focus on non-model protists in future for promoting the study of protists gene duplication.