Mast seeding means that the plants of a population have a highly variable seed production in different years synchronously, and it is widely existed in perennial plants. The periodic variation of seed yield and synchrony of seed production among individuals are the key characteristics. Several hypotheses, including evolutionary bases and limitations of mast seeding, were reviewed in this paper. Moreover, the synchronous degree among individuals was discussed, and the temporal permanence and spatial heterogeneity were emphasized.