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In order to understand the freezing and thawing alternation process of soil and the response mechanisms to hydrothermal factors in the alpine meadows further, the soil temperature and moisture observation data of different soil layers from 1 August 2014 to 1 August 15 are used to study the dynamic characteristics of the soil temperature and moisture at different soil depths in the freezingthawing periods over alpine grasslands in the southern pastoral area of Qinghai Province. The results show that the soil freezingthawing duration of alpine grasslands in the southern pastoral area of Qinghai Province generally can be divided into 4 stages: early freezing, early frozen period, stable frozen period, and thawing period. Soil temperatures in different soil layers varied as cyclical fluctuations with the change of air temperature, and the amplitude decreased with the increase of the soil depth. In addition, the fluctuation of soil temperature and moisture in surface and subsurface layers was relatively bigger, and the sensitivity of the subsoil to hydrothermal factors was weaker. The number of completely frozen days ranges from 44 to 115, and the daily soil freezingthawing alternation process mainly occurred in the surface soil. Soil freezingthawing alternation is conducive to the soil water retention, and has a vital role in advancing the reviving dates of grassland vegetation and promoting the primary productivity.