Abstract: The existing problems when the lysimeter is used in a freezingthawing period are considered in this paper and data of the frozen soil and soil water potential of the experimental station are used. The rule of the permafrost development and its moisture migration are also explored. By analyzing data of lysimeter in the sandy soil at different buried depths and in different years, the lysimeter data processing method and the critical point of buried depth in the freezing period and thawing period are obtained. The results are of important instruction value for usage of lysimeter data of the freezingthawing period.