In this work, the pure polyacrylonitrile (PAN) nanofibers and PAN/$FeCl_3$ composite nanofibers were prepared by an electrospinning process. Electrospinning solution properties including viscosity, surface tension and conductivity, had been measured and combined with the results of Scanning electron microscopy (SEM), Atomic force microscope (AFM) and Micro Combustion Calorimeter (MCC) to investigate the effects of $FeCl_3$ on the structure, surface morphology and combustion property of electrospun PAN nanofibers, respectively. It was found from SEM images that the diameters of composite nanofibers were decreased with the addition of $FeCl_3$, which was attributed predominantly to the increased conductivity of the polymer solutions compared to viscosity and surface tension. The AFM analyses revealed that the surface morphology of electrospun nanofibers changed from smooth and wrinkle-like structure (without $FeCl_3$) to rough and ridge-like structure (with $FeCl_3$). The results characterized by MCC showed that the loading of $FeCl_3$ decreased the heat release rate (HRR) and improved the combustion property of composite nanofibers.