Abstract: By research and practice of corn hybrid seed production, it Studied and analysed the many kinds of cause that bring asynchronous flowering period during corn hybrid seed production. It pointed out the predictable methods of corn flowering period, such as predictable methods of leaf-age, observed method of visible leaf, unsighted leaf and young male spike differentiation etc. It is important to instruct corn seed production and improve the seed yield that these methods are applied to corn hybrid seed production.