Abstract: Longan trees often were harmed by the severe low temperature in winter,even to die.It is very important to study the indicators of freezing injury to Longan trees for the low temperature forecast and reasonable planting distribution.The data of the low temperature in winter and the occurrences of the low temperature damage to Longan trees of Fujian Province in recent years were investigated.The literature on the freezing injury of the Longan trees and the low temperature were reviewed.The photo data of the freezing damage of Longan trees in 1999-2000 in the ten counties in Guangxi provided by Guangxi Meteorological Disaster Mitigation Institute were referenced.The freezing damage grades of Longan trees and the coinstantaneous lowest temperature data in wooden screen were statistically analyzed.The correlation analysis results showed that the grades of freezing damage to Longan trees could be divided into five grades,namely no freezing injury,light freezing injury,medium freezing injury,severe freezing injury and extremely severe freezing injury.The corresponding maximum temperature was by-0.2,-1.6,-2.6,-3.3,and-3.5℃ for the different freezing injury grades respectively.Furthermore,with the increase of the freezing injury grades,the differences of the average temperature for the different freezing injury grades decreased.

Key words: Longan trees, Longan trees, Freezing injury grade, Lowest temperature, Correlation analysis, Indicator of freezing injury