Abstract: Ultra-dry seed storage is a convenient, high-efficiency and low-cost storage method which can conserve high germination ability for a long time at room temperatures. For large grain seeds, it is difficult to be dried to the ultra-dry levels. To detect the ultra-dry adaptability of large grain seeds such as maize seeds and to select the optimum drying method, the hybrid Nongda 108 and inbred Huang C were ultra-dried by vacuum freeze drier and oven and then used for germination tests. The results showed that the vacuum freeze-drying had a much higher drying rate than oven drying. The freeze-drying can dry the seeds to the ultra-dry moisture content within a very short time, and the ultra-dried seeds by freeze-drying show much stronger aging-resistant capability. The germination ability of ultra-dry seeds was lower by directly testing and prehumidification treatment can significantly improve the germination ability of ultra-dry seeds. It indicates that maize seeds are fit for ultra-dry storage, but it must be prehumidificated before sowing.