Under artificial culture conditions, we observed the whole process of gametophyte development of Drynaria roosii Nakaike in Polypodiaceae by scanning electron microscopy in order to reveal some fine structures in different stages of the gametophyte in three dimensions, and provide the evidence for further supplement of classical morphological theory. The results were as follows: (1) two rhizoids of prothallium metrocytes were earliest and simultaneous formed in the process of spore germination. (2) Most rhizoids of the gametophyte of D. roosii were bulging and bifurcate with two cell walls, and the base of the rhizoids was round. (3) The trichomes extensively developed in venter and margin of prothallium, mastoid and acicular singlecelled trichome mixed together. (4) When the antheridia released sperms, the anterior and posterior dehiscence of the cover cells were different. (5) The cytomembrane which attached clastic materials, might be restrictive structure from the sperm to the antherozoid. (6) The disintegration process of ventral canal cells started from the membrane of archegonium opening. (7) It was found that the abnormal archegonium, sex organ that did not distinguish between male and female and sex organ which were vesicular and abortion.