Abstract: Based on data of the daily minimum earth temperature stations from 1958 to 2008,it studied the tenancy trend inclination of frost and unusual events in Datong in recent 50 years using the linear-trend estimation and normal distribution theory.It showed that the date of frost appearance happened late for 1.8 days every 10 years using the linear-trend estimation,the data of frost disappearance happened early for 1.7 days every 10 years,and the frost-free period lengthen for 3 days every 10 years.The characteristics of the unusual frost events demonstrated that there was a high probability that Datong's first frost happened relatively late,and the last frost happened relatively early and the frost-free period had been lengthened,all of which happened after the 1980s with a growing trend while other unusual events happened with a decline trend.On the basis of global warming,it was significance to predict and prevent local frost through analyzing the characteristics of frost climatic variation.

Key words: Datong city, Daily minimum earth temperature, Frost events, Change trend