Abstract:The O-SEBS/PPO composite was prepared by using SEBS- g -MA as coMPatibilizer and melamine cyanurate (MCA) and aluminum diethylphosphite (ADP) as co-flame retardants, and its flame retardancy and mechanical properties were studied. The results show that when the amount of SEBS-g-MA is 5.6%, the amount of ADP/MCA is 1/3, and the total amount of ADP/MCA is 30%, the vertical combustion grade of UL94(mm) reaches V-0, the oxygen index is 29%, the elongation at break is 525±23%, the hardness is 69±1A, and the tensile strength is 6.80±0.1MPa. Thermogravimetric analysis (TGA) and cone calorimeter test(CONE) showed that the addition of ADP/MCA and SEBS-g-MA increased the initial decomposition temperature and the amount of carbon remaining, and decreased the peak heat release rate (PHRR), total heat release rate (THR), smoke generation capacity (SPR) and total smoke generation capacity (TSP). Keywords:Melamine cyanurate;Aluminium diethylhypophosphate;Flame retardant; Styrene-Ethylene-Butylene-Styrene