The stages of fertilization and early grain development are important for determining maize grain number and grain weight, and the periods are sensitive to environmental changes. The maize fertilization consists of 5 processes, including the dispersal of mature pollen, the identification of pollen and filaments, the pollen tube extension in transmitting tract, the release of spermatocyte from eggs and the combination of spermatocyte between eggs and central polar nucleus. The fertilized polar nucleus needs to undergo free?nuclear?phase, cellularized and cell differentiation to form the endosperm, and the fertilized eggs also need a series of division and differentiation to form embryo. The previous period of fertilization is sensitive to the adverse environment, the maize form the abnormal sexual organs under stresses, meanwhile, affecting the pollen and silk vigor fertilization process. The stresses happened in the fertilization process mainly hinder the identification of pollen and flower silk and slow down pollen tube extension rate in the filament. At the early stage of grain development, the fertilization polar nuclei and fertilization eggs are divided and differentiated to form the endosperm and embryo, respectively, suffer the adverse environment will decrease grain storage capacity by hindering the endosperm cell division. A large number of researches have also shown that stresses affect maize fertilization and early grain development through influencing the carbohydrate metabolism and hormone synthesis.