Trisomy 18 syndrome is one of the most common autosomal aneuploidy disorders. Little is known about the genetic regulation leading to the clinical phenotypes associated with the occurrence and development of trisomy 18 syndrome disorders (e.g., mental retardation, cardiac and renal abnormalities). To explore the regulatory factors that influence the phenotypes of the disease, this study used single-cell ATAC sequencing to analyze transcription factors in the accessibility chromatin regions of the single-nucleus cells of the cord blood from 18-trisomy syndrome and control subjects. A single-cell library constructed by capturing 11,611 cells identified seven major immune cell populations, and the results of cell number statistics suggested the presence of abnormalities in the immune system of 18-trisomy syndrome patients. Fourteen transcription factors (P 1.2) were identified by analyzed accessibility chromatin regions. The relative expression levels of four of these transcription factors (TEAD1, TEAD2, TEAD4, Twist2) were confirmed using real-time quantitative fluorescence PCR. In conjunction with information from the literature, this study suggests that these four transcription factors may be associated with abnormalities in cardiac and skeletal development in patients with the 18-trisomy syndrome, thereby providing candidate molecules for mechanistic studies on the occurrence and development of the 18-trisomy syndrome phenotypes.