Abstract: Objective To investigate the amniocentesis amniotic fluid chromosomal examination technique in prenatal diagnosis by analyzing the results of chromosomal detection of amniotic fluid in the second trimester of pregnancy.Methods From June 2013 to December 2017, the pregnant women with high-risk prenatal serological screening, advanced age (aged between 35-42 years old), Bdisplay abnormal fetal or other factors (such as adverse pregnancy history, abnormal family history, etc.) required prenatal diagnosis in our hospital. They were performed amniocentesis in amniotic fluid during 18-24 weeks of pregnancy. The inspection results of them were analyzed.Results A total of 203 cases of amniotic fluid participating in the test, fetal chromosomal abnormalities were detected in 22 cases, the total detection rate was 10. 83%. Among the results, the proportions of cases with high-risk prenatal serological screening were 6. 12% (6/98), advanced age were 8% (4/50), B-display abnormal fetal were 37. 5% (9/24), and other factors were 9. 67% (3/31).Conclusion The abnormal chromosome number and chromosome structure with large segments of the fetus can be detected by amniocentesis of amniotic fluid. It is the "gold standard" for the prenatal diagnosis of fetal chromosome disease.