Abstract: Objective To evaluate the application value of chromosome copy number variation sequencing ( CNV-seq) technology in prenatal diagnosis of elderly pregnant women. Methods A total of 1 395 amniotic fluid samples were collected from pregnant women who were adnmitted in the M edical Genetics Center of Gansu Maternity and Child Health Hospital during January 2018 and December 2019 and undenvent amniocentesis simply because of elder age, and were performed CNV-seq based on high-throughput sequencing.Then, CNV data were annotated using ClinVar, DECIPHER, OMIM and DGV database, the pathogenicity of CNV was evaluated according to ACMG, and relevant reports were retrieved through PubMed database. Results A total of 30 chromosomal aneuploidy abnommalities, ineluding 18 cases of trisomy 21, 2 cases of trisomy 18, 8 cases of sex chromosome aneuploidy ( containing 2 cases of chimerism) and 2 cases of other autosome aneuploidy , were detected, and the detection mte was 2. 15%(30/ 1395). A total of 19 pathogenic CNVs ( pCNVs) were detected, and the detection rate was 1.36%( 19/1 395). Thirty-seven copy number variations with unknown clinical significance ( VUS CNVs) were detected, and the detection rate was 2.65%(37/1 395). There were 48 benign CNVs (B CNVs), and the detection rate was 3.44%( 48/1 395). Conclusion CNV-seq technology can improve the detection rate of chromosomal abnormalities in elderly pregnant women. In addition, the combined application of CNV-Seq and karyotype analysis technology has very important clinical significance in the prenatal diagnosis of elderly pregnant women.