The invention discloses an equivalent method of aperture for hole between clay particles, and provides a complete soil-water characteristic curve by fitting. Data of matrix suction which is between 144000kPa-0kPa are selected, the matrix suction is converted into relative humidity RH, mass water content is converted into volume of water for filling holes in soil per unit mass, Kelvin radius is calculated, real hole radius and thickness of water membrane are calculated, an average hole radius is calculated, and then a equivalent capillary diameter of soil is calculated, and finally a maximum capillary height is calculated The complete soil-water characteristic curve is used as a carrier, based on the prior research and a lot of experiments combined with statistics theory, the equivalent method of aperture of soil sample containing different clay particles, thereby providing a favorable approach for calculating the maximum capillary height.