Abstract: This paper reviews on several typical models for the stochast ic soil moisture dynamics and the corresponding soil moisture probability density functions(PDFs)derived analyticaly,and analyses the effects of random fluctuations,climates, soil,plants and terrain characteristics on soil moisture PDFs based on the modeling results Meanwhile,some experiments are cited in the paper to validate the results obtained from the models. It is showed that the soil moisture PDFs,which response remarkably to all those mentioned factors,is an instrumental tool for revealing soil moisture dynamics and explaining ecohy drolical phenomena. The last part of this paper suggests areas worthy of further research:developing more realistic stochastic models,quantitative describing water stress on plants with stochastic models;coupling soil moisture dynamics and nutrient dynamics,and building soil moisture PDFs for a region and directing the related eco hydrolical work and research with the estab lished soil moisture PDFs.