Abstract: The flowering process of Petunia hybrida was divided into five phases:former differentiation stage(without flower bud),forming stage for sepal and flower bud,forming stage for pistil and stamen,mafure for ovary and anther and anthesis.The petunias with three kinds of colors were chosen,i.e.,pink color,variegated color and red color.During the second phase,the contents of nucleic acid for the three kinds of flowers rose remarkably.During the 4~(th) phase,another peak of the contents of nucleic acid occurred for the pink petunia.The specific activity of DNase in the pink and variegated flowers exhibited the tendency of lowering;and the specific activity of the pink flowers had a peak during the 2~(nd) phase.During the 3~(rd) phase,the specific activity of RNase of the red and variegated flowers appeared a peak;while the pink flowers had a peak in terms of RNase,during the 2~(nd) phase and the 4~(th) phase.The contents of chlorophyll were all lowered for the three kinds of flowers and rose in the 3~(rd) phase and the 5~(th) phase.