土壤热状态是指示多年冻土存在及其热稳定性的最关键指标。为探究黄河源头区冻土热状态的较长期变化，首先构建了土壤热传导数学模型并基于HYDRUS-1D模型求解，经参数率定验证，表明该模型具有较好的可靠性和适用性，然后利用中国区域地面气象要素驱动数据集（CMFD）驱动模拟了黄河源头区6个钻孔1979—2018年冻土地温的变化。结果表明，黄河源头区冻土热状态在1999年发生转变：1999年前温度变化速率为-0.037~0.026 °C/a，1999年后升温速率为0.006~0.120 °C/a。分析表明1998年的气候变暖突变及1999年的极端气候灾害突变是黄河源头区冻土地温在1999年发生突变的主要原因；冻土地温升高，冻土热稳定性下降，将深刻影响冻土水源涵养功能。该研究可厘清高原冻土对气候变化的响应规律，为加强黄河源头区生态环境分区管控提供科技支撑。

The thermal regime of soil is vital for determining the presence and thermal stability of permafrost. To study long-term changes in the permafrost thermal regime in the Headwater Area of the Yellow River (HAYR), a mathematical model for soil heat transfer to simulate the dynamics of ground temperatures at six boreholes using the HYDRUS-1D model. The model’s reliability and applicability were confirmed through parameter calibration. Changes in the permafrost thermal regime from 1979 to 2018 in the HAYR were then simulated using monthly air temperature data from the China Meteorological Forcing Dataset (CMFD). Model simulations revealed an abrupt change in the mean annual ground temperature in the HAYR after 1999. Prior to 1999, the changing rates were from -0.037 to 0.026 °C/a, whereas after 1999, they ranged from 0.0059 to 0.12 °C/a. The abrupt increase in mean annual air temperature in 1998 and the occurrence of extreme climate disasters in 1999 were identified as the primary reasons for the sudden changes in the permafrost thermal regime in 1999. The rise in permafrost temperature and decrease in its thermal stability are expected to impact water resource conservation and biogeochemical cycles. This study provides scientific and technological support for understanding the response patterns of plateau permafrost to climate change and strengthening the zoning and control of the ecological environment in the HAYR.