Abstract: Ceratopteris thalictroidesL.Brongn.was treated with different concentrations of brefeldin A（BFA）for 10,20,30 h,respectively and the resin sections were observed by optical microscope and electron microscope.On this basis,the periodic acid schiff reaction（PAS）and Sudan black B reaction were carried out.The results showed that in the control,the egg of C.thalictroides in the middle stage of development was larger,the nucleolus was round,and the organelles such as Golgi body and endoplasmic reticulum were complete.The fertilization pore between egg and ventral canal cell was clearly visible and there was only a small amount of vesicular secretion in separation cavity between them.Egg membrane was thick with distinct layers.However,under the treatments,the fertilization pore and egg membrane were not typical,which were composed of a large number of vesicles with different sizes.There were more mitochondria and a few Golgi body under fertilization pore;membrane organelles such as Golgi body and endoplasmic reticulum,etc.were broken.A large number of osmiophilic vesicles were distributed above nucleus and below egg membrane and the separation cavity was filled with flocculent substances.Tissue localization showed that separation cavity of the control was empty,while those of treatments were full of polysaccharides.In conclusion,BFA could damage membrane organelles such as endoplasmic reticulum and Golgi body,etc.,affected the normal function of secretory system first and then the formation of egg membrane and fertilization pore.The results of this study lay a foundation for further study on the mechanism of fertilization pore formation and the reproductive biology of ferns.