Objective To evaluate the polymorphism and forensic applicability of Y - DNA STR locus DYS391. Method 111 unrelated male samples from Guangzhou Han population were investigated.DYS391 primer was labeled with FAM. PCR products were detected using denatured PAGE with GenScan Software on the ABI Prism 377 DNA sequencer.Results Frequency data of 3 different DYS391 alleles were obtained. Conclusion The results demonstrated that the DYS391 locus is of high human specificity. No mutation was found.