The spring meteorological data from 1978 to 2015 in the Dandong area are used to analyze the extent of crop damages, which are divided into three different levels, because of low temperature, overcast or rainy weather, as well as scant lightingThe Lagrange interpolation method is used to calculate the expected crop output, and the separation method is used to separate the yield loss caused by the above mentioned weather Results show: (1) The yields of rice and soybean in the Dandong region show significant staged changes(2) The effects of low temperature and rainy weather on crops are : maize＞soybean＞riceThe effects of low temperature and scant lighting weather on crops are different: soybean＞maize＞rice In addition, the influence of rainy and cold rainy weather on corn and soybean is much larger than that on rice