Four halogen-containing compounds，decatbromodiphenyloxide (DBDPO)， chlorinated paraffin-70(Cl-70)，polyvinylchloride(PVC) and chlorinated polyethylene(CPE) were conbi-ned with antimony trioxide(Sb2O3

) to constitu e flame-retardents of polyethylene．DSC and TG investigations show that conbustion of PE is thermal oxygenolysis process through free ra-dical reaction．Halogen-containing compounds decompose and release HX，which reacts with Sb2O3 to give SbX3，before PE burning．These sabstances can retard the conbustion by catching free radicals．△Td，temperature difference betw．en thermal oxygenolysis of PE and decompo-sition of halogen-containing compound，is defined to evaluate the efficiency of the flame-re-tardent．Retardents with proper values of △Td have higher efficiency than those wizh too large or minus values．Among four compounds used in this paper，DBDPO and Cl-70 are effective flame-retardents

while PVC and CPE are of lover efficiency．