Abstract:The variation trend, abrupt change and anomalous years of annual and seasonal me an soil temperature at shallow layers during the period of 1961－2005 in Lhasa w ere investigated by using modern statistical diagnostic methods such as linear t rend analysis, accumulated variance and signal noise ratio methods. The main res ults are as follows: (1)In terms of linear trend, theseasonal mean soil temperature at shallow layers displayed a significant increas ing trend in Lhasa in past 45 years, and it indicated an increase of (0.43～0.60 ℃)/10a which was maximum in spring, minimum in summer. Also, the annual mean so il temperature at shallow layers had a significant increasing trend, and the ris ing rates were (0.45～0.66℃) /10a, specifically at the depth of 40cm. Compared t o the air temperature, the rising range of soil temperature at 40cm was larger i n the same period. (2) The inter decadal variations of the annual and seasonal m ean soil temperature in the shallow layers had an obvious increasing tendency fr om 1960s to 1990s, especially in winter and spring. The mean soil temperat ure was colder from 1960s to the middle of 1980s, but it was warmer from the end of 1980s to 1990s. (3) The abrupt change of mean soil temperature at di fferent shallow layers occurred in autumn of 1986, and all the abrupt change of winter appeared in 1984.(4) Except for the annual mean soil temperature at 40cm was anomalously high in 1999, anomalous lower years occurred in the 1960s at the other shallow layers. Therefore, the increase of the soil temperat ure was mainly caused by the significant increase of air temperature.