Abstract： Objective To determine the value of spectral karyotyping(SKY)in identification of the marker chromosome.Methods Selected six cases that could not be identified in clinic were studied,using samples of peripheral blood from four cases,and samples of amonic fluid and fetal cord blood for prenatal diagnosis in two cases were investigated.All cases were analyzed with the routine SKY method.and the results with the SKY View software.The SKY results were identified by using fluorescence in situ hybridization(FISH).And C-banding technique was used to help diagnose the heterochromatin.Results SKY wag successfully performed on all of 6 cases.The origin of all marker chromosomes was identified by SKY.Except case No.4,the others were confirmed by FISH.It helped determine the pregnancy outcome in two cases of prenatal diagnosis:one case of genetic marker chromosome continued the pregnancy,and another case of de novo marker chromosome was terminated of the pregnancy.Conclusion SKY may be a vahable tool to diagnose the marker chromosome with rapidness,direct-viewing and sensitiveness.It can be used to assess the prognosis and the pregnancy outcome.