Abstract:Karyotypes and Giemsa N banding patterns of 13 species of different ploidy wheats have been studied by means of a new method of preparing mitotic chromosome sample in plant. Chromosomes of all diploids and Emmer are metacentric chromosomes, while submetacentric chromosomes occur only in T. timopheevii and T. aestivum. The number of satellite chromosome in the polyploid wheats is not the case of the amount of diploid. Diploid species do not show any N-bands except for T. speltoides. The banding pattern of T. timopheevii is different from that of Emmer. According to the results, authors consider: 1. In the evolution of polyploid wheats, certain variances arise frmn morphological and structural variation of chromosomes; 2. T. speltoides is of importance to the evolution of polyploid wheats and may not only involve the origin of the B genome but also the G genome; 3. The origin of the B genome perhaps is polyphyletic, i.e. 2 or more amphidiploids included T. speltoides crossing each other result in the present of B genome by recombination or chromosome substitution, and 4. T. dicoccoide and T. timopheevii may have evolved from a common ancestor.