Existence of rock fragments in soil makes it more difficult to measure water content of the soil.Some researchers take rock fragments as fine soil or impermeable media for the convenience of calculation,but this may lead to big errors in some situations.Analysis of these errors was conducted.Indoor experiments were carried out to validate the formula for calculating relative errors.Results indicate that the relative error in measuring water content of fine soil or soil-fragment mixture media was related to rock fragment content and ratio of water content of rock fragment to fine soil.When the ratio was high,big error may result even if the rock fragment content was low; and when the ratio was very low,high rock fragment content also induced great error.In addition,the ratio was not a constant,but varied with their water contents.Therefore,the hydraulic properties of rock fragments need considering in the study on monitoring accurately water regime and simulating quantitatively water and solute transport processes in fields of stony soil.