Oxynitride phosphor mat consisting of CaSi2O2N2:Eu nanofibers is prepared by electrospinning the fiber precursor and subsequent nitridation. As-prepared fiber precursor is smooth and uniform with a diameter of 400-600 nm. After removing organic templates and nitridation, the fiber morphology is well retained and a smooth phosphor mat consisting of uniform fiber network is obtained. X-Ray diffraction results confirm that a pure CaSi2O2N2 phase can be obtained at low temperature of around 1300 degrees C. Series of experiments simulating the LED working environment are conducted and the results confirm that the CaSi2O2N2:Eu nanofiber mat can keep high transmittance and strong emission intensity at the same time, which can be attributed to the uniform fiber arrangement in the nanostructure. Moreover, a new LED packaging process is attempted by using CaSi2O2N2:Eu nanofiber mat. Different colour temperatures can be obtained by employing phosphor mats with different thicknesses. Phosphor agglomeration in the conventional packaging process is avoided, and the efficacy and light homogeneity of the lamp are significantly improved.