To establish a primed in situ labeling (PRINS) technique which can be more effective in detection of single copy gene.On the basis of traditional PRINS, new reagents and procedures, such as TaqStart antibody, four primers of the sex determining region Y (SRY) gene and TSA(TM) Biotin System were included in detection of the SRY gene. Meanwhile, fluorescence in situ hybridization(FISH) to detect the SRY gene was used as control.Fifty metaphases were scored. PRINS labeling showed signals for the SRY on the Y chromosome at band Yp11.3 in all metaphases. These signals were as distinct as that from results of FISH.This improved method is ideal for rapidly localizing single copy genes and small DNA segments. And PRINS is a cost- and time-effective alternative to FISH.