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Using the frost and daily minimum temperature data from 22 ground weather stations in Qinghai Province from 1961 to 2005, the characteristics of frost variation and the main impact on major crops are studied, especially in the Qaidam Basin. The results show that in the past 45 years over the most parts of Qinghai Province, the beginning date of early (autumn) frost postponed, and the ending date of late (spring) frost advanced, most obviously in the eastern agricultural area and then the Qaidam Basin; frostfree periods extended; in the most part of Qinghai Province, the occurrence frequency of heavy frost reduced and the intensity weakened; the intensity variation of spring frost was more obvious than that of autumn frost; and the climate warming mitigated the autumn frost damage and enhanced the spring frost damage.