To evaluate the conventional cytogenetic methods in genetic diagnosis and prenatal diagnosis in the family with a proband of Angelman syndrome (AS).High-resolution G-banding karyotyping and fluorescence in situ hybridization (FISH) on metaphase chromosomes were performed.Two AS patients and 1 normal fetus in the family were successfully detected by FISH.Our result demonstrated that patient with type I AS could be detected by combining the techniques of high-resolution G-banding and FISH with clinical observation, which would offer accurate genetic counseling information to the geneticists and provide the prenatal diagnosis for the AS family