【Objective】To investigate the distribution of copy number variations（CNV）in monochorionic diamniotic （MCDA）twins with discordant and concordant congenital heart diseases（CHD）.【Methods】MCDA twins with CHD were analyzed with conventional fetal karyotyping and chromosomal microarray analysis（CMA），which was performed with Affymetrix CytoScan HD array.【Results】Between 2010 and 2016，114 MCDA twins with discordant CHD and four with concordant CHD were identified. Among the 114 MCDA twins with discordant CHD，fetal karyotyping was performed in 72 cases. The findings of fetal karyotyping were as follows：five with discordant chromosomal anomalies，one with con? cordant 47，XYY，one with trisomy 21 and 65 with accordant normal karyotype. In the 36 cases with discordant CHD， normal karyotype and normal FISH results for DiGeorge region，the prevalence of discrepant CNV was 5.6%. Uncertain of clinical significance CNV and pathogenic CNV occurred in 2.2%（1/45）and in 2.2%（1/45）fetuses with CHD. With re? gard to the four cases with concordant CHD，fetal karyotype was not performed in one. Normal karyotype and normal CMA results were confirmed in the remaining three cases.【Conclusions】Post-zygotic CNV events in MCDA twins may be asso? ciated with about 5% twin discordant for CHD in the investigated cases.