Si-Fe(12)O(19)/PVP composite fiber precursors were prepared by electrospinning with ferric nitrate, strontium nitrate and polyvinylpyrrolidone (PVP) as starting reagents. M-type strontium ferrite nanofibers are obtained subsequently from calculation of these precursors at 800-1100 degrees C. The composite fibers and M-type strontium ferrite nanofibers are characterized by FTIR, TG/DSC, XRD, SEM and VSM. The diameters for the composite fibers are influenced by the metal salt concentration in solution during the electrospinning process and increase front about 300nm to 550nm corresponding the metal salt concentration in the range from 12.5wt% to 23.1 wt%. The M-type strontium ferrite nanofibers calcined at 800 degrees C for 2h are characterized with a diameter range of 100nm to 150nm, crystalline size around 49nm which will increases with the increase of calcination temperature. The saturation magnetization of M-type strontium ferrite nanofibers tends to increase with the crystalline size increasing. The coercivity increases as the crystalline size less than the critical size of a single-domian of 61 nm while decreases as the crystalline size larger than 61 rim. The M-type strontium ferrite nanofibers calcined at 1000 degrees C for 2h, with air average diameter of about 100nm and crystalline size of around 61 nut, exhibit the best magnetic properties at room temperatures, with saturation magnetization of 68.5 A . m(2)/kg and coercivity of 503 kA/m, respectively.