The stage of selecting a contractor, which contains the most important decisions made by employers regarding the selection of a suitable contractor to carry out projects, requires a lot of attention and attention from employers, especially government agencies. Given the importance and position of protecting the treasury and public resources, executive bodies should always seek to select contractors, suppliers and consultants who perform better than other participants. First, the general and common rules for quality evaluation of bidders. And then we review the specific rules of quality evaluation of each of these two categories under the title of "contractors 'quality evaluation" and "suppliers' quality evaluation".