The experiment was conducted by means of routine paraffinembedded sectioning technique to study the development of embryo and endosperm in Adonis amurensis, in order to define the characteristics of the embryo development and offer some information for the systematic study of Ranunculaceae plants. The results were as follows: (1) the embryogeny is of the onagrad type and the endosperm is of the nuclear type of A.amurensis.The division of primary endosperm nucleus is prior to that of zygote. (2) When the seeds have matured, the seed embryos have not been fully differentiated. They are still in the early stage of globular embryo or in the early stage of heart shaped embryo. Embryo development requires approximately 50-60 d. (3) The morphophysiological dormancy exists in seeds of A. amurensis, and they need afterripening to complete the embryos differentiation and to form cytoledonstage embryos. Under the same condition, the differentiation rate of embryo is quite different.