Polypyrrole(PPy) nanowires were prepared by template-free method electrochemically. The effect of process parameters on the morphology of PPy was investigated. The electrocatalytic effect of PPy nanowire modified electrodes was characterized by its amperometetric response toward nitrate ions. The experimental results indicated that the process parameters of the modified electrodes such as concentration of pyrrole monomer, concentration of support electrolyte (LiClO4), and the pH of buffer solution have significant effects on the diameter the length and smooth of PPy nanowires, and thus have obviously effects on electroreduction current density of nitrate ions. Under the optimized conditions, the PPy nanowire modified electrodes have high electrocatalytic activity toward nitrate electroreduction.