Abstract: In order to verify the synergistic flame-retardant effects of silicon-containing macromolecular compatibilizer in halogen-free flame-retardant systems, using maleic anhydride, silicone rubber and polyethylene as raw materials, a novel silicon-containing flame-retardant macromolecular compatibilizer was prepared by melting graft copolymerization firstly. Then the polyethylene composites were inflaming retarded synergistically by compounding of aluminium hydroxide, magnesium hydroxide and silicon-containing macromolecular compatibilizer. Finally, the effects of silicon-containing macromolecular compatibilizer on limiting oxygen index, parameters of cone calorimetry, tensile properties and microstructures of the composites were investigated. The results show that compared with polyethylene grafted maleic anhydride, when the silicon-containing macromolecular compatibilizer content is 10wt%, the inorganic flame-retardants are dispersed better in matrix resin. With the macromolecular compatibilizer content increasing, the tensile strength of composite increases but the elongation at break decreases. The limiting oxygen index increases to 34.0%, and the peak value of heat release rate and total heat release of burning decrease siginificantly, which means that the silicon-containing macromolecular compatibilizer can not only play a favorable compatible role in the composites, but also shows a better synergistic flame-retardant effect.