Crucian Carp (Carassius auratus)is an important economic fishes in the Dongting Lake water system. In order to realize their cells genetic background, the chromosomes number and karyotype of the wild Crucian Carps collected from the Yuanshui River and Lishui River of the Dongting Lake water system were analyzed one by one using chromosomes of kidney cell-PHA culture in vivo prepared by flame-drying technique. The results show that there are two different ploidy levels Crucian Carps which the chromosomes number are 100 and 150±, respectively in both the Yuanshui River and Lishui River. The karyotype formula of 100 chromosomes is 2N=28M+22SM+28ST+22T, NF=150; and the karyotype formula of 150 basic chromosomes is 3N=42M+33SM+42ST+33T,NF=225. With the 100 wild Crucian Carps from different sample points of the Yuanshui River and Lishui River, the proportion of the triploid Crucian Carps (85%)is sharply higher than that of the diploid Crucian Carps (15%), and the morphological characteristics of the diploids and the triploids have no significant differences (P>0.05). The Crucian Carps with two different ploidy levels coexisting in the same water system will have certain theoretical and practical significance to their evolutionary study and genetic breeding, and the huge reduction of the diploid Crucian Carps suggested that resources protection of them in the sight of chromosome set genetic diversity should be strengthened.