Abstract: The Nile perch(Lates niloticus) naturally distribute in Africa and itwas firstly introduced into China from Egyp t in 2003.Nile perch is a good species for aquaculture, as it has excellent traits with rap id growth, good meat quality and huge potential in internationalmarket.After the fish was imported and stocked in Freshwater Fisheries Research Center, the center staff studied on the biological characters, growth performance, nutritional components and culture system of Lates niloticus, but some important genetic characteristics have not been involved, such as chromosome and other cytogenetical traits.Mandarin fish(S iniperca chuatsi) is a famous domestic species with good quality and belongs to the same family Perciformes as Nile perch.The karyotype of Lates niloticus is firstly reported in this paper and compared with S iniperca Chuatsi.The main propose of the study focused on protection of germp lasm resources, systemic evolution and evolutionary status of Nile perch.Also, some basic date would be provided to discuss the possibility for hybridization of Lates niloticus and S iniperca chuatsi through this study.The mitotic chromosomes and karyotype of Nile perch and Mandarin fish were studied using PHA and colchicine intramuscular injection in the back or abdominal cavity of the Nile perch and mandarin fish.This two species was vivo-cultured and renal tissues were used with short-term culture and treated with air-drying technique referred the method used by Lin Hao-Ran, et al. and a slight imp roved.The data was analysed by using two soft-wares: Micromeasure version 313 and Photoshop 710.The results showed that the karyotype ofNile perch was 2n=48, 2m +4 sm+12 st+30 t,NF=54 and the kayotype ofMandarin fish was 2n=48, 6 sm+12 st+30 t, NF=54.The number of chromosomes was same, and there were no satellites in the arms of all chromosomes in these two species.The Lates niloticus had one pair of metacentric chromosome more than those of Mandarin fish.They all had 6 pairs of sub-telocentric chromosome and 15 pairs of tclocentric chromosome and single arm chromosomeswere abundant.The karyotypes of Lates niloticus and S iniperca chuatsiwere similar,which indicted that these two species had very close relationship1 It is possible to get the hybrid of Lates niloticus and S iniperca chuatsi and gives an academic basic for the cross breeding research. Itmust be mentioned here that the juvenile of Nile perch is very sensitive for injection,most of them were dead after intramuscular injection. It is sure that the ideal results can be got by using adult fish as experimental material.