Abstarct: In this research, the angular distribution of multiple scattering of Gamma photons with 662keV,1332 , 1173 and Cs and Co radioactive source that radiate as parallel rays to the cylindrical scatterer, is simulated and measured by MCNP Monte-Carlo method. Also, this process has been done by Cs source and with Aluminum parts as the Scatterer, experimentally. The scattered photons is observed by the detector that surveyed completely in chapter three and the power of the resolution is computed accurately. The peak of the energy of photons that scattered only one time is determined experimentally and theorically and with a Fortran Code in a energy width that obtained in chapter three. The peak of all of the scattered Energy in the output of MCNP code in depended to this scattered event. It’s observed that the amount of the multiple scatted events, when the energy and the angle of the scattering is constant, firstly increased with the increment of thickness and then it reach to a saturated state. The optimum thickness or on the other word, the saturated thickness for multiple scattering in every angle is determined and the amount of the saturated thickness from simulation is compared with the experimental results.