The mean maximum and minimum temperature series are constructed utilizing the observations along Qinghai-Xizang railway seven stations from 1955 to 2000. It showed that the minimum temperature had been in lower period before 1975, and the lowest one which occurred in 1960's was 1.4℃ lower than normal; it was getting warmer after 1975 and it was 1.4℃ higher than normal in 2000. The maximum temperature was 0.1℃ warmer in 1960's than normal and 0.2℃ lower in 1970's and 1980's than normal, but it warmed up again since 1990's and 0.8℃ over the average in 2000. It is obviously that the temperature increased significantly during the period of 1955 to 2000, particularly the minimum temperature. The variation of future sunspot cycle length(SCL) was predicted by 5 significant cycle periods of the SCL in recent 1000 years, 41, 58, 76, 90 and 200 years, and the Gram-Schmidt method of mean generating function, the result showed that the SCL in the 21^th century will be 1 year longer than in the 20^th century, it will reach the longest cycle of 12.4 years in 2055 and turn to short period of 10.6 years in 2068. Also taking the doubling of carbon dioxide, as a prediction experiment, using the REEP method, the increasing temperature probability along Qinghai-Xizang railway was analyzed comparing with 1990's on the basis of the predicted decadal average temperature, it showed that the maximum (minimum) air temperature will increase 0.4℃ (2.4℃) in future 50 years with the probability 66% (74%); 1.4℃ (6.9℃) in 2001 with 85% (62%).