To overcome the agglomeration tendency of nanosilver composite hydrogels and to improve their anti-mold properties, a method of preparing N-isopropylacrylamide/acrylic acid/nanosilver composite hydrogel was developed using the free radical polymerization method. The composite hydrogel was characterized via infrared spectroscopy, dynamic light scattering, transmission electron microscopy, and X-ray photoelectron spectroscopy in order to explore the effects of the acrylic acid content on particle size and dispersion properties of the composite hydrogels. The elemental composition, microstructure, and anti-mold properties of the bamboo strips treated with the composite hydrogel were also determined. The results showed that the composite hydrogel prepared using the novel method described in this study had good dispersity. Composite hydrogels with the smallest particle size and optimized dispersion were produced when AAc concentration was 0.64 µL/mL. The composite hydrogel effectively filled and covered the bamboo cells after treatment. Moreover, it displayed good anti-mold properties as well as retaining the color of the bamboo.