Abstract: Magnesium hydroxide (MH) is a widely used green flame retardant in polymer modification, flame retardant efficiency of which is low. Synergistic flame retardant is one of the main methods to improve its flame retardant efficiency. In the paper, research progress of MH in synergistic flame retardancy is reviewed, and current application status of MH synergistic flame retardants is summarized.Compounding methods and synergistic flame retardancy mechanisms of MH and synergistic flame retardants as well as effects of synergistic flame retardants on mechanical properties of composites are also briefly introduced (42 references cited).