Based on the normal temperature at the urban Nanjing(1960～1990),the variation of air temperature in the urban forest of Nanjing is analyzed using data measured daily at two meteorological observing stations(an urban site and an open site of the ecological station) from 1988 to 2001.It was also described by the normals,annual range,monthtomonth difference,amplitude of the monthly variation etc.During the past 14 years the means of the air temperature in an open site of the urban forest are always lower than the urban site in the monthly means(0.2～1.5 ℃) and annual ranges(0.2～0.6 ℃).The annual variations of the air temperature at two site have analogy with the normal temperature,it is the hottest in July and the coldest in January.The yeartoyear variations of the annual and seasonal means and the abnormal phenomena of the monthly means are analogy at two sites.The cooling effect of the forest area is more remarkable in the nighttime than that in the daytime.