Abstract: 【Objective】 The period from 1950s to 2007 was divided into two stages, i.e., 1950s-1980 and 1981-2007, then the geographical shift of northern limit for citrus planting areas and the possible risk of freezing injury after the shift were analyzed and compared. 【Method】 Using the standard of China farming system regional planning and some agro-meteorological indicators, the geographical shift of safe northern limit for citrus planting areas were compared and analyzed and the change chart was draw by ArcGIS. Using the risk assessment standard of freezing injury, the venture of freezing injury of citrus planting areas after geographical shift were evaluated. 【Result】 Compared with the results during the period from 1950s to 1980, the average geographical shift of northern boundary for optimum planting areas, suitable planting areas, sub-suitable planting areas, possible suitable planting areas is northward 0.75°, the region of maximum geographical shift is sub-suitable planting areas, the next is suitable planting areas, optimum planting areas, possible suitable planting areas, respectively. The extent of northward shift to the east section of northern limit is obviously larger than west section. The average geographical shift of southern boundary for optimum planting areas and suitable planting areas is northward 0.56° and 0.42°, respectively. The largest increment of areas occurs at optimum planting areas, the next is suitable planting areas. Unable planting areas decreased mostly, the next is possible suitable planting areas and sub-suitable planting areas, respectively. The light and middle freezing injury to the sensitive region of optimum planting areas and suitable planting areas show obviously increase than that of their nonsensitive region, and the occurrence frequency of severe and extra severe freezing injury in sensitive region and nonsensitive region is low. The occurrence frequency of light freezing injury in sub-suitable planting areas and possible suitable planting areas for sensitive region is lower than that of their nonsensitive region, but the risk of freezing injury for severe and extra severe freezing injury of sensitive region is obviously increased than that of their nonsensitive region. 【Conclusion】 The northern limit has shown an obvious northward moving under global warming. The risk of freezing injury of sensitive region for citrus planting areas after the northward shift is obviously higher than that of nonsensitive region.

Key words: climate warming, subtropical crops, northern limits, risk of freezing injury, China