[Objective] To analyze the spatial and temporal characteristics of the soil moisture variation in vadose zone in order to provide basis for the study on the "four waters transformation" dynamic cycle.[Methods] Using the concept of the potential energy of soil water dynamics, the characteristics of the moisture in vadose zone and changes in water potential with time and depth was studied.[Results] The significant difference was observed in soil water potential distribution in each season. Soil water potential reached the highest in June and August, even got saturation in some blocks. On the contrary, it dropped to a minimum in period from December to next March. Soil moisture of 50 cm depth was affected greatly by seasons and water potential changed dramatically. Yet soil moisture below 50 cm depth was substantially independent of the season changes. And between 50-140 cm depth water potential was relatively stable; Beneath 140 cm, it was only influenced by gravity potential.[Conclusion] The factors such as rainfall, irrigation, evaporation, groundwater depth and others could cause the changes in the profile distribution of soil water potential, thus causing changes among a variety of soil water movement states.