Polymer is easy to burn when heated, which may result in fire disaster. Thus, it is necessary to improve the flame retardant performance of polymer by employing flame retardants. Layered double hydroxide (LDHs) has attracted more and more attention in the field of flame retardant due to its halogen-free, non-toxic and excellent smoke suppression performance. In this paper, the structure, preparation methods, and flame retardant mechanism of LDHs were summarized. In particular, the methods to improve the flame retardant properties of LDHs, including cationic doping of laminate, interlayer anion intercalation, and surface modification, were emphatically reviewed. Moreover, the flame retardant mechanism and properties of LDHs with different structure were concluded. At last, the development trend of LDHs as flame retardant in the future has prospected. The aim of this paper is to provide guidance for the development of LDHs flame retardants and related researchers.