YF3:Eu3+ nanofibers, polyaniline (PANI) and ferroferric oxide (Fe3O4) nanoparticles (NPs) were incorporated into polyvinyl pyrrolidone (PVP) and electrospun into Janus nanofibers with YF3:Eu3+ nanofibers/PVP as one half side and PANI/Fe3O4/PVP as the other half side. The morphology and properties of the final products were investigated in detail by X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, energy dispersive spectrometry, Hall effect measurement system, fluorescence spectroscopy, vibrating sample magnetometry and UV-Vis spectroscopy. The results reveal that the [YF3:Eu3+/PVP]//[PANI/Fe3O4/PVP] trifunctional Janus nanofibers possess excellent electrical conduction, magnetism and fluorescence due to their peculiar isolated nanostructure. Fluorescence emission peaks of Eu3+ are observed in the [YF3:Eu3+/PVP]//[PANI/Fe3O4/PVP] Janus nanofibers and assigned to the D-5(0) -> F-7(1) (587, 595 nm), D-5(0) -> F-7(2) (614, 622 nm), and the D-5(0) -> F-7(1) magnetic-dipole transition at 595 nm is the predominant emission peak. The electrical conductivity reaches up to the order of 10(-4) S cm(-1). The luminescent intensity, electrical conductivity and saturation magnetization of the Janus nanofibers can be respectively tunable by adjusting respective amounts of YF3:Eu3+ nanofibers, PANI and Fe3O4 NPs. The new type trifunctional Janus nanofibers have many potential applications in the fields of electromagnetic interference shielding, microwave absorption, molecular electronics and biomedicine. More importantly, this design concept and construct technology is of universal significance to fabricate other multifunctional nanostructures.