The soil that we studied is located on the Jiulian mountain natural reserve of Jiangxt province, and is under the evergreen broad-leaved forest. It is a moumainouns soil. We deter-mined the physical properties and the seasonal dynamic change of soil moisture (for one year in succession) of the soil, and with these data we analysed the water retention ability of the soil.The soil possesses good physical properties: the soil texture is mainly loamy clay and clay loam, the bulk density is small (0.88-1-29), the porosity is large (51.7-65.4%), the permeable velocity is fast (17.4-142.8cc/min), and the maximum moisture holding capacity is high (occupying 50.6-58.2% Of the volume).The drainage of the soil is good, and the moisture of the soil is sufficient. The moisture content is more than 30% in most part of the year. The annual ranges of moisture content are: 0-15cm layer, 26-56%; 15-30cm layer, 26-45%; and 30-50cm layer, 26-45%.We analysed the water retention ability of the soil with the dafa of prermeable velocity and maximum moisture holding capacity of the soil, and compared it with the red soil of the hilly land, the results are as follows: the permeability is 3-5 times as much of the red soil; the capability of absorbing rainfall is 219% of the red soil.