Abstract: Based on the daily minimum temperature data at 20 meteorological stations in NingXia during 1961-2010, the frost days were calculated according to the climatic index on frost. Using climatic diagnosis methods，characteristics and change trend of frost days were studied. The results showed that the average number of frost days was 10.4 times each station every year. The spring frost days accounted for 58%, autumn frost days accounted for 42%. In the three regions，the sort order of the frost days was Yellow River irrigation area＜Middle Dry area＜South Mountain area. In recent 50 years, the total frost days, spring frost days and autumn frost days all showed the decreasing trend. Change trends of three regions were all similar with that of the whole autonomous region. Decadal variation showed that，before the 1980s, frost days were more than the average of 50 years, and after 1980s, frost days were less than the average of 50 years. Three regions’ decadal characteristics of frost days were similar with that of the whole autonomous region. Mutation of total frost days occurred in 1986, mutation of spring frost days occurred in 1991, but of autumn frost days occurred in 1974. In the background of global warming in the last 50 years, the frost days are in decline in NingXia. The study can provide a basis for the meteorological service of frost in Ningxia.