Abstract: Two male mule ducks with sexual behavior and seven female ducks with different development reproductive organ were selected from a herd of F1 ducks crossbred from Beijing duck (♂) and Muscovy duck (♀).The experiments of anatomy, histology and cross showed that intergeneric hybrid duck didn’t lose their fertility completely; The agenesis of F1 duck ovary was the direct reason for the low reproductivity; The different karyotype in Pair 1 and Z chromosome of Muscovy duck and Beijing duck was the major reason for infertility in their F1 progenies.