... Computation of the polarization properties of RATAN-600 with taking into account diffraction effects . ... The paper describes the Muller matrix elements for RATAN-600 computed with the allowance for the diffraction effects in the space between the primary and flat mirrors in the Souther sector with a flat reflector ("South+flat") observing mode and in the mode of single-sector observations at the horizon throughout the entire operating wavelength range. ...