A thin coding metasurface was produced with 8*8 random configurations formed of two elements, encoded as element “0” and element “1”, with a phase difference equals to 180±30° in a broad frequency band from 28 to 40 GHz. An optimal coding metasurface allowed to reduce the monostatic and bistatic Radar Cross Section (RCS) below -10 dB from 28 to 40 GHz when compared to a perfect electric conductor (PEC) plate with same size. The coupling effect produced between the elements has been reduced. The optimal random coding metasurface was designed by using an efficient method of minimization called "pattern search" with the help of planar array theory, and simulated by means of the CST Microwave Studio software.