Abstract: In order to evaluate the influence of agricultural climate resources, including light, heat and moisture, on grain crops during the summer drought, the author adopted the evaluation method of the phototemperature potential and the photo- temperature- water potential of grain, comparatively analyzed potential deviations of climate mean state to the grain production during summer drought, objectively and quantitatively analyzed advantages and disadvantages of agricultural climate resources during summer drought in Guizhou. The results showed that: the photo-temperature potential of rice and corn during summer drought compared with the normal climatic year was generally higher of 10%, light and heat resources had obvious advantages; but the photo-temperature-water potential of rice and corn during summer drought compared with the normal climatic year generally was lower of 30%-40%, water resource disadvantages limited crop growth. Through the rational development and efficient use of water resources to meet the crops demand of water during summer drought, good light and heat conditions were more conducive to agricultural production.