In order to know the feature of frost event in Chongqing under the back of global warming, and provide more reference for optimizing agricultural planting structure, the variation characteristics of frost in Chongqing was analyzed by using surface observe data day by day of Chengkou meteorological station, and applying statistical method. The results showed that: (1) In recent 40 years, the first frost and the last frost also occurred later, the rate of the first frost was faster more than the last frost. The frost-free period present longer trend slowly. Since 21 century, the later trend of the first frost and were increasing, while the frost-free period was decreasing. (2) The change of intensity of the frost was gradual, but the last frost was stronger more than the first frost. Since 21 century, no matter what the first frost nor the last frost, its intensity became weaken. (3) In recent 40 year, the first frost, the last frost, and the frost-free period all showed apparent decadal and periodic change characteristics. The first frost had about 30 years periodic, while the last frost has about 23 years periodic. The trend of deviation from normal of the first frost was at first increasing and then decreasing, but the last frost was decreasing continuously. Since 21 century, the rate of extreme later of the first frost was increasing. (4) As a whole, the number of abnormal year of the first frost was more than the last frost. But since 21 century, abnormal degree became more serious. So only know regular of the frost, improving duly agricultural planting structure, people could improve the quality of agriculture industry.