Poly(styrene-co-N-isopropylacrylamide)/poly(N-isopropylacrylamide-co-methacrylic acid)/polypyrrole-silver [P(St-NIPAM)/P(NIPAM-co-MAA)/PPy-Ag] composite microgels were synthesized via a one-step redox polymerization of silver ammonia ions and pyrrole monomer at room temperature, using the core-shell P(St-NIPAM)/P(NIPAM-co-MAA) thermo-sensitive polymer microgels as templates. The structure, component, and properties of the as-prepared composite microgels have been characterized by transmission electron microscope, Fourier-transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and UV-Vis spectrophotometer. The results indicate that the size and the dispersity of the formed PPy-Ag nanocomposite particles can be regulated by adjusting the initial concentration of the precursors. The catalytic activity for the reduction of 4-nitrophenol was regulated by varying the environment temperature. Meanwhile, the higher catalytic activity is contributed to the electron transfer from the conductive polymer PPy to the Ag nanoparticles in the polymer material matrix.