Abstract: In this paper, we researched the karyotype of the bullfrog Rana catesbeiana. The result proves that the number of chromosomes is 2n=26 in the bullfrog Rana catesbeiana. Five pairs of large chromosomes and eight pairs of small chromosomes can be divided into three groups A , B and C. There is no differences of sex chromosome between individuals of two sexes. The secondary constrictions appear on the chromosomes of No.7，8，10 and 12. The karyotype of the bullfrog Rana catesbeiana is that K (2n) = 26 = 22m + 4sm .