Abstract: The research of the evolution principle of frost-free period would give climate resources support for risk decision making in agriculture.In order to determine the impact of them on agriculture,the formation and variation principle of frost-free,frost date were analyzed with regression in Excel.At the 56y(1953-2008) series,the last frost date of Chaoyang advanced 17d,the first frost date postponed 12d,frost-free period extends 27d.In the past 20 years the last frost damage deceased to 10%.Early frost damage reduced by 80%.Frost period variation increased the heat resources.Because of the instability of frost date,the increased use and development of energy resources,there were some risks,which could be considered in facility agriculture.Frost still remained one of the local meteorological disasters.Mastering frost principle,making accurate forecast would be the foundation of the local agricultural decision-making.

Key words: Frost, Evolution, Risk measures, Chaoyang