Abstract: Malus pumila cv. Fuji (2n)、Malus pumila cv. Jonagold (3n) and Malus xiaojinensis Cheng et Jiang (4n) of apples were used as the materials in the experiment. The content of nucleic acids of the floral buds of the different ploids in apples were compared. During the differentiation processes dynamic changes of nucleic acid of the floral buds of the ployploids in apples were almost the same as that of diploid. But at the same differentiational stage, the contents of DNA、RNA and the total nucleic acids were obviously improved in the foral buds of polyploids of apples. Compared with the diploid, the numerical value of RNA/DNA of floral buds of triploid was increased, but the extent of increasement was very small, whereas the numerical value of RNA/DNA of floral buds of tetraploid was decreased obviously.