Abstract： Objective The authors aim to provide genetic counselling and prenatal gene diagnosis to the families with osteogenesis imperfecta(OI), based on the identification of pathogenetic mutations in large cohort genetic testing. Methods DNA was extracted from the peripheral blood of parents of the fetuses, and from the villi tissue, amniotic fluid or cord blood of the fetuses using a standard sodium dodecyl sulfate-proteinase K-phenol/chloroform extraction method. PCR combined with Sanger DNA sequencing was performed to validate the pathogenic mutations of 200 fetuses at risk of OI and their parents from 158 families. Allelic analysis of microsatellite markers was applied to exclude the false positive caused by maternal DNA contamination, when both the fetus and the mother harbored the same pathogenic genotype. Results A total of 83 affected fetuses (83/200, 41.5％) and 12 (12/200, 6.0％) recessive carriers were identified among the 200 fetuses. The 83 affected fetuses included 78 heterozygotes (45 of COL1A1, 32 of COL1A2, one of IFITM5), and 5 compound heterozygotes or homozygotes of recessive OI (two of FKBP10, one of SEC24D, one of WNT1 and one of CRTAP); The 12 recessive carriers included 7 of WNT1, 4 of SERPINF1 and one of SERPINH1. Maternal DNA contamination was excluded from the genomic DNA samples of OI fetuses when their mother with the same affected genotypes. Conclusion In this study, the authors used an optimized gene diagnosis system of OI to perform prenatal genetic diagnosis to 200 fetuses at high risk of OI, and provided precisely genetic counselling to the OI families.