Abstract: The paper reviewed the development status of flame retardant technology for unsaturated polyester resins (UPR) from 1992 to 2018 and also introduced the additive-type and reactive-type flame retardants specially used for UPR. The additive-type flame retardant included inorganic nanoparticles, inorganic fibers and relevant modified compounds and in-situ polymerization flame retardants, and the reactive-type UPR flame retardants covered a variety of Si-, N-and P-containing monomer. Moreover, the flame retardant effects and associated mechanisms were also discussed.