In vitro experiments indicate that the flower color pigment of Prunus mume Sieb.et Zucc.’Nanjing Hongxu’(Nanjing red-bearded) is intense purple in methanol containing 1% HCl and the color is stable at pH 0～3.The pigment expresses colorless,blackish green or yellow-green because it is sensitive to light,heat,oxidant,reductant or chelating agent.It also expresses various red,purple,blackish yellow,blackish red or faint bluish green because of different metal ions or different concentrations of the ions.Glucose and low concentrated sodium beneoate almost have no effects on the pigment color.Sucrose can weaken the color,but citric acid can strengthen it.This paper could be a reference or a premise for the exploration on the flower color mechanism,the identification of the molecular structures of the anthocyanins and the exploitation and utilization of the flower color pigments of the red Mei flowers.