Abstract: This research was aimed to study the soil physical properties,the soil water characteristics and their influences on the plant available soil water in a mixed forest of Pinus tabulaeformis and Quercus variabilis in the Xishan Mountain.The soil had good physical properties as follows:soil density is 1.20～1.45 Mg·m^-3,total porosity,45%～58% while the non-capillary porosity,6%～10%,and the root is in poor aeration.The soil moisture characteristic curve could be described by the Gardner empirical equation θ_v=ΑS^-B.The soil had a water holding capacity of 418.77 mm while the field water holding capacity was 348.53 mm and the soil wilting capacity 34.01 mm.So the soil had a field water holding capacity of 314.52 mm.But on site study it was showed the actual water holding capacity never reached such high level.The actual water storage was 60～180 mm,much lower than the field water holding capacity.There existed an about 50 days dry period from late of April to the early of June with the soil moisture lower or near 10%.There existed a humid period from July to early of September with a soil moisture between 15% and 20%.In other period the soil moisture was 10%～15%.

Key words: soil physical properties, soil moisture characteristic curve, soil wilting capacity, soil storage