Cubic spline function was used to assess soil water distribution,and then further to calculate soil water diffusivity.From the experiments,it was found that the soil water diffusivity estimated with the method mentioned above was close to that obtained with the classic Bruce and Klute method except when soil water content was near saturation.The whole process could be done quickly with the aid of a computer program without the trouble of freehand drawing.Therefore,the method is a simple workable one for calculation of soil water diffusivity.