The chromosome number and karyotype of Pseudorasbora parva were analyzed using a routine method including intraperitoneal injection of PHA and colchicine,cultivation in vivo,and slides preparation with air-drying.Whilst erythrocyte nuclear DNA content of P.parva was determined by using a flow cytometer (Beckman Coulter Inc.,USA) with serving the chicken erythrocytes (their DNA content is 2.30 pg) as reference cells.Results obtained in this study showed that:the diploid chromosome number of P.parva was 50 (2n=50); the karyotype of this species was 2n=18 m+22 sm+10 st,NF=90,while the secondary constriction,heterosome and satellite chromosome were not observed; the diploid cellular DNA contents of P.parva was 3.18 pg,which was 1.38 times to the chicken erythrocytes’.