Abstract: Abstract: Based on the daily minimum temperature data at Taiyuan meteorological station from 1951 to 2008, the first and late frost events occurrences series were established respectively. Basic characterics were analyzed by using statistical method and the change trends of them were analyzed by using the linear method and the unusual frost were also analyzed by comparing them with criterion. The results were listed below: (1) The first frost event occurred on Oct. 14th, the late frost event occurred on Apr. 15th and the frostless season was 182d on average. (2)Comparing with the average date, the first frost events occurred early in 1950s, 1960s and 1990s, normal in 1970s,late in 1980s and early 21st century; the late frost events ended late and frostless seasons were short in 1950s-1970s.After 1980s, they were early and long (3) The first frost events occurred towards a late trend obviously(2.2d/10a), the last frost was a ahead trend(-1.8 d/10a) and the frostless season was longer and longer. (4)The frequency of unusual first frost events took up 17.2% (including 1.7% for earliest and 15.5% for earlier respectively) and that of unusual late frost events took up 12.1%(including 5.2% for latest and 6.9% for later respectively).