Abstract: Based on the historical precipitation data of eleven counties and cities in Jinzhong from 1972 to 2006 and the different climatic and geographical environment,Jinzhong City was divided into four sub-regions.Using the mathematical statistical method,the spatial and temporal distribution features of the grain reduction in different regions caused by summer drought were analyzed.The influence of the summer drought on maize production in four different kinds of years,such as high yield years,crop failure years,drought years and normal years,was analyzed as well.The reasons of the drought formed and eased in each growing period of maize were discussed.The results showed that in significant drought years,the average influence of the grain reduction was by 23.5 percent to 42.3 percent,while in disaster years,the average reduction of the whole Jinzhong City was by 1.05×108 kilograms to 3.50×108 kilograms.In the five disaster years of the whole city,the reduction of maize was to 1.095 billion kilograms.The drought losses occupied 65 percent to 84 percent in all the city's disaster losses.The frequency of drought was increasing and the intensity of drought was growing,which led to increase of the years of maize yield reduction.

Key words: Drought, Drought, Maize yield, Assessment, Anomaly percentage