Based on the observation data from meteorological stations in Sanjiang Plain from 1951 to 2020, linear trend analysis and correlation analysis were used to explore the temporal and spatial variation of soil freeze-thaw characteristics in the area and their correlation with meteorological factors. The results show that: (1) Temporally, the maximum freeze depth in the Sanjiang Plain shows a decreasing trend at a rate of −0.8376 cm/a. The soil freezing time shows an overall delayed trend, while the thawing time shows an advancing trend, jointly leading to a shortening of the freeze-thaw cycle. (2) Spatially, the maximum freeze depth decreases radially outward from the Baoqing station. The initial freezing and thawing timing advances from east to west, stable freezing is delayed from northwest to southeast, while stable thawing advances from northwest to southeast, and the freeze-thaw cycle progressively shortens from northwest to southeast. (3) The process of soil freezing and thawing has a short overlap in some specific periods. The freezing process responds most significantly to changes in negative accumulated temperature, with a correlation coefficient of −0.86. The correlation coefficients of soil thawing depth with daily average temperature, positive accumulated temperature and daily maximum temperature were 0.77, 0.88 and 0.72, respectively, indicating a multi-dimensional response of thawing depth to temperature variations, with the strongest correlation observed for positive accumulated temperature.