Abstract: This paper examined the relationship between the spatial and temporal distribution characteristics of the maximum depth of frozen soil,air temperature and ground temperature in Beijing over the past 40 years.Data from six meteorological observation stations in Beijing from 1981 to 2021were collected,including daily maximum depth of frozen soil,average air temperature,average ground surface temperature and the ground temperature data at the depths of 5,10,15,20,40 and 80 cm.The results indicated that the maximum depth of frozen soil generally became shallower from west to east across the meteorological observation stations,with a climate tendency rate of-2.3 cm/10 a.The maximum depth of frozen soil in Beijing showed a weak correlation with ground surface temperature and a stronger correlation with ground temperatures at the depths of 40 and 80 cm.By selecting the comparative test data of frozen soil in Beijing from 2021 to 2022,this study revealed that the instrument demonstrates better agreement with manual observation of frozen soil after one freezing and thawing cycle.The data quality of the temperature measurement type for frozen soil automatic observation equipment was directly influenced by the subterranean rock formations and soil distributions at the installation location.After the instrument achieved stable operation,it was necessary to optimize the algorithm and the threshold value for freezing and thawing in accordance with the local conditions.