Abstract: Based on the observed climate data at eight agro-meteorological observation stations in Qinghai Province,the beginning phases of freeze and thaw of soil surface were analyzed.The results showed that beginning freeze and thaw phases had an obvious regional difference.The freeze phases in number of stations had a shortened trend,while it prolonged in Huzhu and Delinha.The changes of the beginning phases of freeze were obviously influenced by climate change.When the mean air temperature from March to September increased by 1℃,the beginning phases of freeze delayed by 1.57.5 days,averagely by 2.3 days,except for Guide,Nuomuhong and Huzhu;When the mean air temperature from October of last year to February of next year increased by 1℃,the thaw phase were 213days earlier,averagely 2.3 days,except for Menyuan and Delingha.When the rainfall increased by 10mm,the thaw phase delayed by 26 days,averagely by 2.3days,except for Nuomuhong 12 days delayed.When the mean air temperature from October of last year to February of next year increased by 1℃,the number of days from beginning freeze phase to thaw phase were shortened by 2.423.1 days,averagely by 1.8 days,except for Guide,Henan and Menyuan.

Key words: Beginning freeze and thaw phase, Beginning freeze and thaw phase, Climate change, Response