Based on the temperature, precipitation, and soil moisture and temperature data of the alpine meadows in the Qinghai Lake Watershed from 2018 to 2020, the characteristics of soil freezing and thawing in the alpine meadow ecosystem and the daily changes and seasonal dynamics of soil temperature and moisture in different freezing and thawing stages were analyzed. The results showed that:1) Based on the analysis of the characteristics of soil temperature changes, the freeze-thaw cycle process could be divided into the initial freezing period, the complete freezing period, the thawing period and the complete thawing period. The duration of each stage was as follows:complete thawing period>complete freezing period>thawing period>initial freezing period. From surface to deep soil, the number of days of complete melting continued to increase, and the number of days of complete freezing tended to decrease. The period of complete melting of 0-180 cm soil layer lasted for more than half a year. 2) Frozen soil showed the law of one-way freezing and two-way melting. The soil melting rate (5.45 cm/d) was faster than the soil freezing rate (2 cm/d). Throughout the freeze-thaw process, the changes in soil moisture at different depths were more complex than changes in temperature. 3) With the freeze-thaw cycle process, soil temperature and moisture showed periodic seasonal changes. The diurnal variation of soil temperature and moisture was consistent, and the surface layer had a large diurnal range. As the depth increases, the diurnal range became smaller and tended to be stable. The structural characteristics of soil profile had a strong explanatory effect on the heterogeneous distribution of soil moisture.