To determine the change of the mechanical properties of the wool/polyester blend fabrics in proportion to blend ratio, 16 mechanical properties were measured on G blend fabrics by KES-F system. Blend ratio on the 6 blend fabrics was increased by 20% and the structure of the fabric were plain. 2/2 twill, respectively. And wearing performances in proportion to blend ratio on the 6 blend fabrics were investigated. In this experiment, the following conclusions were obtained with the increase of blend ratio of polyester. 1) The values of WT, RT in tensile properties, tensile energy and elongation, and RC in compressional properties were decreased. 2) The values of B, 2 HB in bending properties, 2 HG, 2 HG 5 in shearing properties were increased. 3) Putting on clothes, wearing performance was bad because crumbling of shape and wrinkle were easily made an appearance. Particularly it was remarkably bad as blend ratio of polyester was expressed 60%.