Abstract: This paper reported the p rocess of fertilization in Brassica campestris ssp. pekinensis and its duration of each stage. The results are as follow: 1. Pollen germinates on stigma 2 - 3 h after pollination. 2. 4 - 8 hours after pollination, pollen tube grows in style. 3. 8 - 14 hours after pollination, pollen tube grows in ovary and gets into ovule via micropyle. 4. 16 hours after pollination, one sperm nucleusmoves to egg and enters it. 5. The sperm nucleus adheres to the nuclearmembrane of egg 18 hours after pollination. 6. 20 hours after pollination, sperm nucleus enters egg nucleus and male chromatin gradually disperses and 24 hours after pollination, male nucleolus appears. A large female nucleolus and a smallmale nucleolus occur in the nucleus of fertilized egg, and zygote formed. The dispersing of sperm chromatin in egg nucleus takes about 4 hours; 7. 32 - 34 hours after pollination, the division of zygote begins. The dormancy stage of the zygote lasts for about 8 - 10 hours; 8. The pair polar nuclei lie in chalazal end to egg before fertilization, which fuse into a secondary nucleus or not; 9. 16 - 18 hours after pollination, the sperm nucleus moves to the polar nuclei or the secondary nucleus. 18 hours after pollination, sperm nucleus adheres to the nuclearmembrane of polar nuclei or that of the secondary nucleus; 10. 20 hours after pollination, sperm nucleus enters one of the polar nuclei or the secondary nucleus and the triple fusion takes place. The process of fusion is similar to the karyogamy, and faster than that. The dispersing of the sperm chromatin in polar nucleus or secondary nucleus takes about 2 hours; 11. 22 hours after pollination, the primary endosperm nucleus formed. The female and male nucleoli can not fuse with each other before mitotic division of the p rimary endosperm nucleus; 12. 24 hours after pollination, the division of the p rimary endosperm nucleus takes place.

Key words: Brassica campestris ssp. pekinensis, Fertilization