Abstract: At present, the research on permafrost in Beijing is relatively rare.Based on the data of seasonal frozen soil, air temperature and ground temperature from 1975 to 2017 at Tanghekou National General Meteorological Station in the northern mountainous area of Beijing, this paper studies the relationship between seasonal frozen soil and climate change in Tanghekou.The results show that in the past 43 years, the air temperature has exhibited the opposite trend to global warming, and the ground temperature in 0-80 cm layer also shows a decreasing trend.The change of seasonal frozen soil in Tanghekou is contrary to the conclusion that the seasonal frozen soil in China shows a shrinking trend.In Tanghekou, the maximum frozen soil depth is deepened, the first freezing day is advanced, the thawing day is delayed and the frozen soil days are increased.And by mutation test it is found that the mutation of the air temperature during Tanghekou permafrost season occurred around 1988.In addition, the mutation of the maximum permafrost depth occurred between 2007-2009, and the depth showed a significantly deepening trend after the mutation.Considering the phenomenon of global warming stagnation, it is found that during 1998-2012, the air temperature in Tanghekou frozen soil season decreased significantly at a rate of -1.29℃/10a, and the frozen soil deepened significantly at a rate of 21.893 cm/10a.The remarkable cooling trend of Tanghekou in recent 20 years may be an important reason for the development of frozen soil in the area in recent 43 years.