Abstract: In order to provide some scientific basis for the agricultural production and disaster prevention and mitigation in Liaoyang City, based on the daily minimum temperature date at Liaoyang Meteorological Station from 1956 to 2010, the impact of frost on the cropper at Liaoyang was analyzed and the characters of frost were studied by using the linear trend method. The results showed that: (1) the average dates of first and the last frost events were October 13th and April 16th, and the average frost-free period was 179 d. (2) It was found that the dates of first frost event delay with decade, while the last frost event advance overall, and the last ones delay only in 1980s. (3) The linear trend rates of first and last frost events and the frost-free period were 1.7 d/10 a, -1.2 d/10 a and 3.0 d/10 a, and the change trends of them were all significant above 0.05. (4) There was scarcely effect of frost in the normal years on the cropper, but in some years, the first or last frost events might occur in the period before the rice mature or the period of maize seedling-coming, and people should prevent it.