The law of the variation of the soil water in low Taihang mountainous areas of gneiss ofHebei province as well as the effect of terraced and trenched field with slope on the law were studiedby means of fixlocation experemental observation and resonant wave analysis.The results showedthat the variation of soil water content showed obvious periodicities because of the effect of precipi-tation and evapotranspiration,etc.Terraced and trenched field with slope increased the average valueof the soil water content seqence,reduced variation,delayed maximum and minimum value and en-hanced drought resistance because of thick soil layer,high accumlation of runoff and retaining wa-ter.