Abstract: Sex differentiation is an important stage in plant ontogeny. The clarification of its mechanism is of importance to the developmental biology both in theory and in practice. Genetic markers, especially the protein and molecular markers developed in recent years, are playing more and more important role in elucidating the mechanism of sex determination. With comparison of genetic bases of various flowering systems, this paper reviews the studies of various genetic markers including morphology, protein, isoenzyme and molecular marker and their application in plant sex determination. The advantage and disadvantage of different marker systems are briefly discussed.