The combustion degradation process of rigid polyurethane foam, the flame retardant mechanisms of flame retardant and the common flame retardants for rigid polyurethane foams were reviewed. The latest development of flame retardants in the rigid polyurethane foam was summarized. The synergistic effects of addition-type flame retardants and between addition-type and reactive-type flame retardants were also emphasized.The future development prospect of flame retardants in the rigid polyurethane foams was elaborated.