A kind of inorganic-organic hybrid semiconductor composite nanoparticles: Dawson-type phosphomolybdate-doped polypyrrole(P_2Mo_ 18-PPy) was designed and prepared using microemulsion oxidation-polymerization at room temperature and characterized by TEM and IR. The P_2Mo_ 18-PPy was used as a bulk-modifier to fabricate a chemically modified carbon paste electrode(CPE) by direct mixing, which represents the example of polyoxometalates(POMs)-doped semiconductor polymer nanoparticles modified electrode. Both the advantage of POMs-doped polymer and the surface-renewal property of the CPE were fully utilized. The electrochemical behavior of the P_2Mo_ 18-PPy bulk-modified CPE(P_2Mo_ 18-PPy-CPE) was investigated with cyclic voltammetry. Three couples of reversible redox peaks were observed in the range from +800 to 0 mV, which corresponded to the reduction and oxidation through two-, four- and six-electron processes, respectively. The P_2Mo_ 18-PPy-CPE showed a high electrocatalytic activity for the reduction of nitrite, which expanded the application of POMs-doped semiconductor polymer nanoparticles. A kind of inorganic-organic hybrid semiconductor composite nanoparticles: Dawson-type phosphomolybdate-doped polypyrrole (P 2 Mo 18-PPy) was designed and prepared using microemulsion oxidation-polymerization at room temperature and characterized by TEM and IR. The P 2 Mo 18-PPy was used as a bulk-modifier to fabricate a chemically modified carbon paste electrode (CPE) by direct mixing, which represents the example of polyoxometalates (POMs) -doped semiconductor polymer nanoparticles modified electrode. Both the advantage of POMs-doped polymer and the surface-renewal The electrochemical behavior of the P_2Mo_18-PPy bulk-modified CPE (P_2Mo_18-PPy-CPE) was investigated with cyclic voltammetry. Three couples of reversible redox peaks were observed in the range from +800 to 0 mV, which corresponded to the reduction and oxidation through two-, four- and six-electron processes, respectively. The P_2Mo_18-PPy-CPE showed a high electrocatalytic activity f or the reduction of nitrite, which expanded the application of POMs-doped semiconductor polymer nanoparticles.