Abstract There were two kinds of basic chromosome number, x=10 and x=11, in the polyanthous daffodils(Narcissus tazatta L.).The basic chromosome number x=10 with two kinds of karyotype, one was typical bimodal, i. e., all the chromosome in a set fall into two sharply defined classes, 6 long and 4 short ones; the other one was non-bimodal with 4(or5) long, 2 medium and 4(or3)short chromosomes in a set. The basic chromosome number x=11 was a non-bimodal or non-typical bimodal karyotype with 4(or 5)long, 2 medium and 5 (or 4)short chromosomes in a set.The bimodal karyotype of x=10 was an original one. The x=11 was derived from the original karyotype(x=10, 2n=20) by increasing a pair of short m chromosomes after reciprocal translocation of unequal chromosomal segments in two pairs of long chromosomes (No. 5and No. 6). The other one, x=10 2n=20, new non-bimodal karyotype may be a result of loss the short m chromosome from the x=11 2n=22 karyotype or combination of the male and female n gametes without the m chromosome after translocation.