Abstract: The karyotype and chromosome number of Acacia holosericea, were analysed on meristematic cell of root tips The result showed that the chromosome number in each somatic cell was 2 n=4 x=52 (tetraploid) According to the classification made by L C Saylor, the Karyotype formula is K(2 n)=4 x=52=44 m+4 sm+4 st According to the chromosome length<2 μm, the chromosome of Acacia holosericea belongs to a small chromosome.