The part of Yellow River in Inner Mongolia was chosen as a typical area of Yellow River Basin. The regional annual average maximum temperature (AMaxT), annual average minimum temperature (AMinT) and annual average temperature (AvT) from 1951 to 2012 were selected and analyzed by Mann-Kendall method. The temperature variations before and after the mutation and the warming stagnate following the mutation were also discussed. Annual (or seasonal) AMinT mutation happened first on 1977 to 1987. Then the AvT and AMaxT mutation happened on 1978 to 1993 and 1978 to 1994, respectively. The mutation period of average autumn and winter temperature were same as AMaxT. The earliest intra-annual mutation was winter (1977 to 1978), and the latest was summer (1987 to 1994). The winter and AMaxT had more variations than summer and AMinT. The increase ratio or AMinT was 0.231~0.604℃/10a which have the most contribution. All the annual (or seasonal) temperatures had a warming stagnate from 1997 to 2007 after the mutation, successively. The stagnate occurred in spring and not stagnate occurred in summer. Mostly annual and seasonal temperature stagnate happened later than the global period which winter firstly, then autumn, the AvT was the last one (on 2007). The AMaxT increase rate was lower in the period of after mutation and before stagnate. However, the decrease rate of AMaxT if faster after stagnate. The AMinT was on the contrary. This indicates that the AMinT was sensitive to temperature increase and the AMaxT was sensitive to the temperature decrease. In seasonal, the spring AMaxT increase rate is higher from mutation to stagnate, and the spring AMinT decrease rate was the fastest after the temperature stagnate which is -0.324℃/a.