In order to determine the position of the fixed point of the new jig fastening piece and ensure that the blockage ratio is reduced to the minimum and the wind cup group is also in the optimal uniform field, on the basis of testing the optimal uniformity region of the test wind field, the threedimensional model of the threecup anemometer is established by using CAD, and the maximum frontal area in the rotation process of the threecup anemometer was calculated. Finally, the blockage effect test experiment is carried out to verify it. The results show that the error of the traditional estimation is corrected by calculating the frontal area based on CAD, and the blockage ratio of the optimized test wind field is 0.04, which is reduced by 42%, and the indicated wind speed of the test wind field and the indicated wind speed of the free wind field are almost the same.