Abstract: In order to investigate the mechanism of soil moisture dynamics during cucumber crop cultivating,the main factors of weather and the water pressure in soil were monitored. From the experimental data, the formulae of variation of the root length and the leaf area index of cucumber with time were fitted, and then the models of evapotranspiration and transpiration under the condition of cucumber cultivation were obtained. Afer that, the numerical model of water movement in soil was established based on the theory of soil water dynamics. By simulating the moisture dynamics in soil during initial and flourishing fruit stages, the results showed that the mathematical models were in good agreement with the measured data. In addition, the influence of different irrigation amounts and different initial moisture contents on soil water movement was analyzed.