The 1-hexyl-3-aminoethylimidazolium tetrafluoroborate ionic liquid [HAIM]BF4 was synthesized and applied to the modification of graphene. The ionic liquids modified graphene (G@ILs) were prepared by combining G powder with 1-hexyl-3-aminoethylimidazolium tetrafluoroborate ionic liquid [HAIM]BF4 via a green and ball milling method. The resulting G@ILs were incorporated into acrylonitrile-butadiene-styrene copolymer (ABS) using a melt blending method to prepare G@ILs/ABS composites. The structure and properties of G@ILs were analyzed using various means such as X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman testing. The results show that [HAIM]BF4 effectively modifies graphene through cation-π interactions and maintains the structural integrity of graphene. The G@ILs/ABS composites exhibited considerable improvement in mechanical properties due to the unique properties of G@ILs. The tensile strength and bending modulus of G@ILs/ABS composite with 1%G@ILs are 42.40 MPa and 2145.01 MPa, which are 8.36% and 12.76% higher than that of ABS. In addition, the thermal conductivity of G@ILs/ABS composite with 1%G@ILs is 0.249 W·m-1·k-1, which is 21.5% higher than that of pure ABS.