Abstract: Using the observation data of ground temperature of 68 stations in the northeast of Tibetan Plateau from 1961 to 2015,statisticing the strength index I(including frequency)sequence of cold air process in spring months,the variation characteristics of regional cooling air frequency and its origins are analyzed by using climate diagnostic method. The results are as follows. On the trend of change,every 10 years,the trend rate of climate change about cold air process frequency in spring from 1961 to 2015 is -0.290,the decrease is not significant. The decreasing trend of Qaidam Basin and southern area as common with the northeast of the Plateau,the increasing trend of eastern area is indistinctive. In terms of periodic variation,the quasi-periodic of 3,5,7,8years are occuredShigh frequency relatively,25 years and other quasi-periodic are occured low frequency relatively. The height value continue on the high(low) side in spring at the 500hPa Baikal is one of the factors to lead cold air process frequency in the northeast of the Plateau continue to be less(more) from 1991 to 2015(from 1961 to 1980). In spring,the high-pressure ridge of Ural Mountain、Balkhash Lake、the low-pressure trough of Baikal、the high-pressure ridge from Caspian Lake to Aral Sea continue to be strong,it is easy to lead the cold air from the north to the south to influence China from the west、northwest and north roads. The northeast part of the Tibetan Plateau is located in the passageway of cold air southward,cold air process frequency more than the normal,on the contrary,cold air process frequency is less.