Imidazolium ionic liquid (IL) and IL/nano silica particles were employed to produce antistatic ultrahigh molecular weight polyethylene (UHMWPE) composites. The UHMWPE/IL/SiO₂ composites were processed by a self-developed elongational rheology extruder (ERE). The influence of IL/SiO₂ content on the processing, electrical,crystallization and mechanical properties of UHMWPE was studied. The results show that IL is a good plasticizer for UHMWPE, and can increase the extrusion efficiency of UHMWPE obviously by reducing the extrusion torque of UHMWPE in the ERE. The addition of IL can significantly reduce the surface friction voltage of UHMWPE from 2.72 kV to 0.04 kV when the IL mass fraction is 3%. It is noteworthy that, loading IL on nano silica particles can avoid the IL blooming on the surface of UHMWPE and promote the uniform dispersion of IL in the UHMWPE matrix. Nano silica particles have a good toughening and strengthening effect on UHMWPE to improve the tensile strength and impact strength of UHMWPE/IL/SiO₂ composites. Compared to the pure UHMWPE, the antistatic UHMWPE in this study has great application prospects in the fields of electronic information and precision device manufacturing.