| The study was carried on in zhuanglang county located in Loess Hilly Reign in three important growth stage (April, July and October). The five forest-grass intercropping models(Hippophae rhamnoides+Medicago Sativa, Pinus tabulaeformis +Medicago Sativa, Pinus tabulaeformis+Onobrychis viciacfolia,Prunus ammoniac+ Medicago Sativa, Prunus ammoniac+Onobrychis viciacfolia)were researched.The variation law of soil water was applied to compare and measure character of soil water in different intercropping models. And analyzed the temporal and spatial dynamics of soil water and Soil water holding capacity. The results as follow:(1) Soil bulk density varied from 1.17 to 1.40g/cm3 and the difference is significant. With soil depth increased, the soil bulk density variation of model one is 1.27～1.38g/cm3. and the maximum is 1.38 g/cm3 in 60cm then declined; Model two reduced and the maximum is 1.40g/cm3; model three reduced and then increased and the minimum is 1.18g/cm3 in 60cm; model four had high soil bulk density in the soil surface, then decreased; model five varied from 1.17 g/cm3 to 1.25 g/cm3 and had drastic variation in 0～80cm and then steady.(2) The variation of general porosity of five models is 49.73%～54.48%. The model five had relatively low general porosity(49.73%). Model five had highest soil general porosity(54.48%). The soil noncapillary porosity of model one and model three increased with soil depth increased, and the maximum are 8.46%and15.24% in 60cm. Soil noncapillary porosity of model two had the maximum in soil surface(11.11%) and decreased with soil depth increased. Model four and five increased and reached the maximum in 40cm, ( 6.46%,5.65%)then decreased .(3) Mode one had higher field moisture capacity than the others in all layers. And the maximum was 36.87%. It decreased with soil depth increased. Model four had the same tendency in 0～60cm but only 18.80% in 60cm. Model two increased and reached the maximum(28.92%) in 60cm. Model three and model five decreased and reached the minimum(22.26%,24.26%)and then increased.(4) Saturated soil water content of five models are significant differences. Model five and model four had higher saturated soil water content than others. The model four had maximum(51.60%) in soil surface. Model one and model two increased with soil depth increased; model three and model four increased and then declined and reached to 16.40%; model five increased and then declined in 0～60cm and had the highest saturated soil water content in 40cm and 60cm . (5) Soil water content of five models had vertical difference in 0～100cm. Model one,two and five decreased with soil increased. 0～20cm is inconstant layer of soil water, 20～80cm is utilized layer of soil water, 80～100cm is the steadily adjusted layer. In model three and model four, 0～60cm is inconstant layer of soil water, 60～80cm is utilized layer of soil water, 80～100cm is the steadily adjusted layer.(6) The seasonal variation of soil water content of all model except model four had the same tendency with local rainfall. It increased and reached the maximum in July , then declined. But model had lowest soil water content in July.(7) Model four had relatively low soil water content in the whole growth season and the temporary dry soil layer appeared in 80～100cm.(8) The soil water content of all models had close lineal relationship with age class and slope. The fixed equation: Y=25.95-0.49X2-0.27X7(Y:soil water content,X2 :age class,X7:slope),R=0.999.(9) The water character curve of five models can be fixed by S = aθ?b. All model had higher soil holding capacity in soil surface and lowest in 60cm. Model five had the highest soil holding capacity. All models soil specific water capacity varied widely. The soil specific water capacity of Model one was 10-2 in the -80KPa suction the water furnishing ability is the weakest. The suction power model five is 14.4～29.5 times than release power in -50 KPa. Model five had the highest suction power and water furnishing ability.(10) The study showed the model five had the powerful soil water furnishing capability and soil water upholding capability.It's the prefer forest-grass intercropping model for vegetation rebuilding.
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