Monodisperse poly (methyl acrylate-meth-acyloxy-ethyl trimethylammonium chloride) cationic nanospheres were synthesized by soap-free emulsion polymerization, and were subsequently combined with gardenia to prepare dye/nanospheres. The influence of the concentration of gardenia yellow, rate of vortexing, temperature and pH of mixing on the adsorption capacity and stability of microspheres were thoroughly investigated, and the prepared gardenia/poly (methyl acrylate-meth-acyloxy-ethyl trimethylammonium chloride) nanospheres acted as liquid pigments to dye the fabric substrates by the impregnation method. In particular, the photostability of gardenia/poly (methyl acrylate-meth-acyloxy-ethyl trimethylammonium chloride) and the reflection of its dyed fabrics are distinctly described, the comparison of the dyeing property effect between gardenia/poly (methyl acrylate-meth-acyloxy-ethyl trimethylammonium chloride) and gardenia yellow dyed by mordant dyeing were analyzed. According to the experimental findings, the dyestuff nanospheres have high stability when the pH is 7–8, the mass ratio of gardenia yellow to poly (methyl acrylate-meth-acyloxy-ethyl trimethylammonium chloride) nanospheres was 12.8:1, the temperature was 60°C for 30 min, and the mixing speed was 500 rpm. Dyeing cotton fabrics with gardenia/poly (methyl acrylate-meth-acyloxy-ethyl trimethylammonium chloride) produced higher color strength and color fastness than the gardenia yellow with mordant dyeing.