The surfactant, sodium dodecylbenzenesulfonate (NaDDBS) and coupling agents, γ-aminopropyltriethoxy sliane (KH550) and isopropyl dioleic(dioctylphosphate) titanate (NDZ101) were used to treat multiwalled carbon nanotubes in this work. The effects of surface modification of multiwalled carbon nanotubes on crystallization behavior, mechanical properties, and electrical properties of low density polyethylene/polyolefin elastomer/multiwalled carbon nanotubes composites were studied. The results showed that NaDDBS, KH550, and NDZ101 had a favorable effect of improving the dispersion of multiwalled carbon nanotubes, but it cannot improve the interfacial interactionbetween multiwalled carbon nanotubes and the matrix. The improvement in dispersion favored the crystallization behavior and mechanical properties. Modified multiwalled carbon nanotubes had a better acceleration nucleation effect than raw multiwalled carbon nanotubes on low density polyethylene/polyolefin elastomer blends at low content (≤1 wt%). The tensile strength of low density polyethylene/polyolefin elastomer/multiwalled carbon nanotubes composites with modified multiwalled carbon nanotubes increased with lower multiwalled carbon nanotubes content (≤1 wt%), and KH550 and NDZ101 led low density polyethylene/polyolefin elastomer/multiwalled carbon nanotubes composites to possess a higher tensile strength than that of NaDDBS with 1 wt% content. NaDDBS, KH550, and NDZ101 had a minor influence on the dielectric properties of the composites and even caused a decrease in the dielectric loss of composites with 10 wt% multiwalled carbon nanotubes content.