It has been shown in this paper that the constant thickness ratio contours for the symmetric multilayers of (A2BA)m type are a series of circular arcs perpendicular to the real axis on the complex amplitude reflectance diagram for the layer A or B. Some of the CTR contours pass through the areas having drastic changes in reflectances. By taking the reflectance change sensitivity to the optical thickness into consideration, a level monitoring scheme for such multilayers with v=- 0.317 or -3.169 is chosen. When the starting reflectance of a precoated subsbrate is given, the monitoring terminationg for the individual layers in the basic layer periods, the monitoring wayelengtlig, as well as the exact oonstruobions of the multilayers are determined with the aid of the refleotanoe diagram technique. During this course, only very simple arithmetic calculations are involved. The measured spaotral trangmittanoe of two symmebric multilayers, produced by using the above monitoring scheme, are very good in accordance with the numerical resnlta of the designed ones.