The invention discloses a modified polyethylene composite nanomaterial. The modified polyethylene composite nanomaterial is prepared from, by mass, 80-90 parts of carbon black modified polyethylene, 100-120 parts of nano-silicon carbide modified polyethylene, 100-120 parts of nano-zinc nitride modified polyethylene, 40-50 parts of titanium carbide modified polyethylene, 30-40 parts of nano-silver powder modified polyethylene, 10-15 parts of carbon fibers, 45-50 parts of teflon, 8-10 parts of chloroprene rubber, 10-12 parts of butadiene rubber, 13-15 parts of butadiene-acrylonitrile rubber, 4-5 parts of silicone rubber, 6-8 parts of polycarbonate, 5-6 parts of tetrabutyl titanate, 10-12 parts of titanium dioxide, 6-8 parts of iron boride and 5-6 parts of calcium silicide. The modified polyethylene composite nanomaterial is high in strength, excellent in heat resistance and flame retardance, good in heat stability and uniform in dispersion, the flame retardance, heat resistance, oil resistance and strength of the composite material are improved, and meanwhile the fluidity and processability of the composite material are improved.