Abstract: The thermo- and pH- sensitive monodisperse poly(N-isopropylacrylamide-co-acrylic acid) (P(NIPAM-co-AA)) nanogel was prepared through emulsion polymerization in aqueous solution using N-isopropylacrylamide (NIPAM) and acrylic acid (AA) as monomers. The hydrogels structure and chemical compositions were characterized by Dynamic Light Scattering (DLS), Atomic Force Microscope (AFM) and Fourier Transform Infrared (FT-IR). The influence of the contents of monomer and emulsifier on the particle size and polydispersity index (PDI) of the hydrogels were studied, and the thermo- and pH- sensitiveness of the nanogel were explored. When the molar ratio of AA to monomer was 20% and the mass of emulsifier was 0.05 g, the synthesized nanogel particle morphology was uniform and neat with the hydrated particle size 403 nm and PDI only 0.033, and the nanogel was sensitive to temperature and pH, especially for pH of 4-6.