Electrospun blend-polyimide (blend-PI) nanofibers with high tensile strength and toughness were highlighted in this article. The blend-PI nanofibers were prepared by electrospinning the binary blend of rigid and flexible polyamic acids followed with thermal imidization. The method is simple and can be extended to the other kinds of polyamic acids. The morphologies and structures of the blend-PI nanofibers were investigated by scanning electron microscope (SEM) and wide-angle X-ray diffraction (XRD). The mechanical properties, thermal properties and miscibility of the blend-PI nanofibers were studied by tensile test, thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The mechanical properties of the blend-PI nanofibers, including tensile strength, modulus, elongation at break and toughness could be well-tuned by modifying the molar ratio of the rigid component (B-PI) and the flexible component (O-PI). The blend-PI nanofibers with B-PI/O-PI molar ratio of 4/6 had the ultra-high strength of 1.3 GPa and excellent toughness of 82 J/g. All the blend-PI nanofibers showed thermal stability of over 500 C. The only one glass transition temperature (Tg) suggested the good miscibility of the binary PIs in the blend-PI nanofibers. This study would open completely new opportunities for modifying the properties of electrospun PI nanofibers.