Abstract: Objective：To explore the feasibility of multiplex quantitative fluorescent PCR (QF-PCR) for rapid diagnosis of the children with Down′s syndrome. Method：The loci of six short tandem repeat (STR) on chromosome 21, D21S1442, D21S1432, D21S11, D21S1435, D21S1412 and D21S1809, were amplified by multiplex QF-PCR. The PCR products were detected by capillary electrophoresis. The polymorphism of STR DNA was analyzed with GeneMapper software. The peripheral blood lymphocytes were cultured and chromosome karyotyping was performed for each case. Results：The sensitivity and specificity of the detection with six STR loci were 99.0% and 100% respectively according to the results of 198 cases with Down′s syndrome. Among the 181 cases of standard type of Down′s syndrome, 180 cases (99.45%) were diagnosable. All the 14 cases of ectopic type of Down′s syndrome were diagnosable (100%). One of the 2 cases of mosaicism of Down′s syndrome was diagnosed, and another special karyotype of Down′s syndrome was found. Conclusion：The detection of multiplex QF-PCR for diagnosis of Down′s syndrome should be time saving and accurate, so it is suitable to be applied for clinical diagnosis since the high sensitivity and specificity.