Abstract: By using records of frozen soil collected from 8 surface weather observation sites in Datong from 1961 to 2008, the date of Datong ground freezing and thawing, the number of freezing days, and the spatial and temporal distribution of maximum depth of frozen soil are analyzed. The results showed that in recent 40 years the freezing date has a delaying trend while the thawing date is ahead of the recorded. The number of ground freezing days has a corresponding decreasing trend and maximum depth of frozen soil decreases from northwest to southeast in successive years. The city’s average maximum depth change of frozen soil over the years has the overall decreasing trend but after 2000, compared with 1960s to 1980s there is an increasing trend.

Key words: Seasonal frozen soil, Distribution, Variation characteristics