Abstract: Based on the daily minimum temperature data measured at 12 meteorological stations over northern Shanxi from 1970 to 2008, the method of modern climatic diagnosis was used to analyze the climatic features of the first and last frost event occurrence and their influence on agriculture. Here are the results: (1) The relation was obvious both dates of first and last frost event occurrence and altitude, the higher the altitude, the earlier the first frost while it was opposite for the last frost.The influence of altitude on the last frost is more evident than on the first frost.(2) Much of the northern Shanxi,the trend was found that the first frost event occurrence was late while the last frost was seen early,but the anomaly between years was remarkable and it can be over 30d.(3) The delaying trend of the first frost mainly began from 21st century, but the decadal change of the last frost was not synchronous, the turning point appeared in 1990s for most representative stations, it was late in 1970s and 1980s,early in 1990s and 21st century. (4) Along with the change of frost event occurrence, the possibility might be drop markedly for early and late stage of maize growth to suffer from frost, it was advantageous for local maize growth.