An original Ag nanoreactor capable of positively temperature-responsive and substrate-selective catalysis was prepared in this study. This nanoreactor was made of Ag nanoparticles encapsulated in a 4-nitrophenol (NP)-imprinted polymer matrix that exhibited a temperature-sensitive interpolymer interaction between poly(acrylamide) (PAAm) and (2-acrylamide-2-methylpropanesulfonic acid) (PAMPS). At relatively low temperatures (such as 20 T), this nanoreactor did not demonstrate significant NP-selective catalysis due to the interpolymer complexation between PAAm and PAMPS, which caused shrinking in the imprinted networks. Conversely, at relatively high temperatures (such as 40 T), this nanoreactor provided significant NP-selective catalysis resulting from the dissociation of the interpolymer complexes between PAAm and PAMPS. Unlike traditional Ag nanoreactors, which lack positively temperature-responsive catalysis or substrate-selective ability, this unique nanoreactor employed both the imprinting of the substrate molecule (i.e., NP) and a temperaturesensitive PAAm/PAMPS network, thereby making positively temperature-responsive, substrate-selective catalysis feasible.