The invention discloses a fetal genetic detection method based on fetal adventitial trophoblast cells of a maternal body. The method comprises steps as follows: 1), a sample containing the fetal trophoblast cells is provided; 2), the sample is fixed, glacial acetic acid is added for digestion, centrifugation is performed, a buffer solution is resuspended, pancreatic enzyme is added for digestion, and a buffer solution is resuspended; 3), a magnetic nanoparticle coupled HLA-G monoclonal antibody is added for incubation; 4), a magnetic frame is adopted for collection, the buffer solution is washed and centrifuged, and cells captured by magnetic nanoparticles are purified; 5), DNA enzyme treatment is executed, a single cell is selected and subjected to single cell genome amplification, and genome DNA is subjected to interruption-based database construction; 6), sequencing analysis is performed. The method is simple, convenient, fast and high in specificity.