【Objective】It is recognized that soil pore size distribution and soil water holding capacity plays an important role in soil aeration and crop root development. This study is to explore changes in water holding capacity and soil pore size distribution induced by the change of land use from paddy field to vegetable field. 【Method】A new method of using the low field nuclear magnetic resonance (LF-NMR) technology was adopted to acquire features of the T₂ spectrum of soil samples collected from the fields full in field moisture capacity, and on such a basis, relationships of amplitude and relaxation time of the signals of the soil samples dehydrating with soil moisture content and pore size distribution were analyzed. 【Result】Results show that pore size distribution did not differ much between paddy soil and facilitated vegetable soil, being quiet scattered, and composed of more small pores than large ones. After paddy field being turned into facilitated vegetable field, soil pores became smaller in diameter and soil structure worse. In the process of the soil losing its water, peak reduction and spectrum shift took place simultaneously. Small peaks disappeared first, with a reduction rate much higher than that of the main peak, indicating that during the process pore shrinkage and water loss of water occurred simultaneously and the water in big pores drained first and then sequentially that in small ones. 【Conclusion】All the findings in the study indicated that the method based on LF-NMR can be used to instantly monitor changes in soil moisture content and more directly and accurately determine soil moisture migration processes and pore distribution rules without disturbing the soil, and hence may serve as new theories and technical support for the study on mechanisms of soil degradation and soil amelioration in facilitated vegetable fields.