We observed the processes of fertilization and embryo development in crosses between ‘butterfly’ (2n=4x=60) and the simple breeding line ‘NH6’ (2n=2x=30) using paraffin section.The results showed that:(1)At 17 h after pollination,pollen tube entered into one synergid and released contents,sperm nucleus got into one of polar nuclei and fused with two polar nuclei to form primary endosperm nucleus.At 1 day after pollination,sperm nucleus moved towards egg nucleus and adhered to the nuclear membrane of the egg cell.Formation of zygote and endosperm free nuclei was observed 2 day after pollination.Development of embryo went through stages of proembryo,globular embryo,heart embryo and torpedo embryo.The hybrid barriers were detected in fertilization and different embryo development stages.Barriers included sperm did not fused with egg or sperm did not fused with polar nucleus,and zygote did not divided,or primary endosperm nucleus did not divided,and embryos aborted.Embryos aborted at different developmental stages (proembryo to cotyledon embryo),but mainly at globular embryo.