The water-dispersed conductive polypyrrole (PPy) nanoparticles were prepared via the chemical oxidative polymerization with fulvic acids (FM), a renewable resource from both soils and municipal waste compost, as dopant and stabilizer for tuning the properties of polypyrrole nanoparticles. The FA-doped polypyrrole (PPy/FAs) nanoparticles were characterized with Fourier transform infrared (FTIR), UV-vis, thermogravimetric analysis (TGA), transmission electron microscopy (TEM), and electric conductivity. The diameters of the PPy/FAs nanoparticles decreased from (150 to 20) nm with the increasing of the feeding ratio of FAs, and the PPy/FAs nanoparticles could be well-dispersed in water. Their electrical conductivities were affected markedly by the amount of the natural dopant added. They have weakly temperature-dependent conductivity over the entire temperature interval from (283 to 423) K.