A novel approach to prepare pH- and thermo-sensitive hollow spheres based on a precipitation polymerization method has been demonstrated.The poly(Nisopropylacrylamide) (PNIPAM) nuclei formed in the nucleation stage played the role of non-cross-linked templates，on which cross-linked poly(N-isopropylacrylamide-co-acid) (P(NIPAM-co-AA)) shells were formed by adding a cross-linker N

N′-methylene-bisacrylamide and acrylic acid to the aqueous solution during the following nucleus-growing stage.A “selfremoving” process was found to take place when the temperature of the reaction solution was reduced below the LCST，where the non-cross-linked PNIPAM nuclei spontaneously penetrated through the cross-linked shells to form the hollow spheres.The hollow structure was confirmed by TEM analysis.The zeta potential analysis indicated that，the shells of these hollow spheres contained carboxylic groups derived from the polymerized acrylic acid.These hollow spheres were characterized by light scattering analysis at various pH and temperatures.The results indicated that these hollow spheres could well respond to the change of pH and temperatures.As the pH increased from 2 to 7，the volume of the hollow spheres with 4.76% and 9.09% AA contents increased by about 12 and 18 times，respectively.As the temperature increased from 25℃ to 40℃，the volume of the hollow spheres with 476% AA content decreased by about 12 times.