With ‘Dianthus hybridus’ as experiment material, we used fluorescence microscope to observe the pollen germination and pollen tube growth after pollination, to study the process of fertilization and embryo development with paraffin section method. The results showed that: (1) at 1 h after pollination, a small amount of pollens germinationed; At 4 h after pollination, a large number of pollens germinationed, pollen tube tips were found in the style middle, and callose response was found in pollen tubes; 6 h after pollination pollen tube grow to capital base and with a small amount of ovules; After 15 h stylar cannal has callose response, the pollen tube with the ovule number increased; At 24 h, many of pollen tubes have arisen around, one of the pollen tube enters the ovule, some pollen tubes have formed coiled overgrowth and generate callose reaction in the embryo sac. Sperm nucleus fused with polar nuclei mainly in 17-48 h after pollination, and the egg cell fusion process is mainly in 1-3 d after pollination. (2) The development of embryo through the proembryo, globular embryo, rod shaped embryo, heartshaped embryo, torpedo embryo and cotyledon embryo stages. (3) Cross obstacle characterized by: only free endosperm nuclear and no embryo developmental embryo sac, zygote did not divided, sperm did not fused with polar nucleus, only free endosperm development without embryos of embryo sac, globular embryo aborted. The prefertilization and postfertilization, obstacle are the main cause of low seed setting rate.