Abstract: This article has introduced the recent progress of the study on the secondary formation and modification of plasmodesmata. The existence of the secondary formation of plasmodesmata on the cell wall was found during the developmental process of plant by means of both counting the changes of the number and density of plasmodesmata in the appointed region of cell wall, and observating the formation of plasmodesmata on the cell wall between scion and stock of grafting union. The secondary modification of the previously-formed plasmodesmata often takes place reversibly in some region at some special stages of plant development. This may suggest that the secondary modification of plasmodesmata would be related to the isolation of symplast and the regulation of assimilate transport during the growth and development of plant.