Triethylamine catalyst was used to increase the molecular weight of poly(amic acid). In electrospinning, diameter of PAA nanofibers was controlled by molecular weight of poly(amic acid) and concentration of poly(amic acid)/N-N dimethylformamide solution. The diameters of polyimide based carbon nanofibers reached to a minimum value of around 100 nm. The conductivity of the carbon nanofiber papers increased with the decreasing of fiber diameters, while the mechanical strength of polyimide and carbon nanofiber paper was diameter independent. Further more, Pt was successfully impregnated in carbon nanofiber. Reduction accompanied with carbonization in Ar gas at up to 1000 degree C produced small and well-dispersed Pt nanoparticles (3-5 nm). Carbon dioxide treatment exhibited the effective ability of removal of carbonaceous overlayers to promise a potential enhancement Pt catalyst activity. The reduction rate of Pt ion is different at heating rate of 2 and 5 degree C/min. Thus, the heating rate and time at high temperature strongly affected Pt nanoparticle size.