The single-scattering-foil method is the basic of passive proton beam spreading system. In this paper, the angular distribution and energy distribution of proton beam on passing through a single scattering foil are calculated using Monte-Carlo multi-particle transport code Fluka2006.3b.2., including the effect of proton energy, scattering material and target thickness on scattering angle. The result shows that thin-high-atomic-number material can be used as the scattering material.