The present invention relates to average properties calculation method of the ground is installed tapered files 100 for ground reinforcement, tapered files 100 average properties calculation method of the ground is provided according to the invention the head portion, the head portion at the bottom consists extension formed konbu and part extending like a tail at the bottom of the cone portion on, as the tapered section file 100 average physical property calculation method of the ground is installed to be embedded in the lower portion of the base bottom that structure is formed, the load of the structure and structure determination step of calculating the area of ​​the bottom base; Equivalent File conversion step of dividing the volume of the tapered file to apply the terms of the depth of the tapered files tapered files into one file, the cross-sectional area equivalent to the uniform; Reinforcement area calculation step of calculating the area of ​​reinforcement being reinforced by the tapered section of the file by multiplying the cross-sectional area and the batch airlift tapered files of the file equivalence; Wonjiban area calculation step of calculating the first wonjiban area to the area in the reinforcement area of ​​the bottom base; By dividing the area of ​​the base bottom, after adding the product of the physical properties of the wonjiban the wonjiban area in the product of the physical properties of the tapered files in the reinforcement area in the average properties calculation step to obtain the average physical properties of the base bottom, the lower and it is composed of the technical features.