Sn K alpha1-detecting Sn K-edge XANES spectrum was successfully measured for Pt-Sn/SiO2 catalyst (2.5 wt% Pt, Sn/Pt atomic ratio 1.0) in the energy resolution 5.0 eV using Rowland-type fluorescence spectrometer equipped with Ge(13,13,13) bent crystal. The Obtained steeper, more clearly resolved XANES spectrum thus obtained could be compared quantitatively to theoretical XANES spectra generated by ab initio calculations for thirteen kinds of plausible Pt-Sn site models (alloy, adsorbed Sn, and mixture models). This spectral simulation suggested the feasibility of that fluorescence-detecting XANES is a simple method to judge the plausible site structure as simple method without detailed spectral analyses. The comparison supported an adsorbed Sn site model structure on highly-dispersed Pt[-Sn] nanoparticles on SiO2.