Phase　change　materials　(PCMs)　are　highly　promising　for　the　digital-storage　technology　based　on　the　fast　phase　transition　between　the　crystal　and　amorphous　states.　In　order　to　optimize　the　properties　of　PCMs,　the　doping　of　PCMs　has　become　research　hot　points　nowadays.　In　this　paper,　effects　of　Sn　doping　(0%,　10%,　30%)　on　the　crystallization　behavior　of　Ge2Sb2Te5　(GST)　films　induced　by　a　picosecond　pulsed　laser　with　Gaussian　energy　profile　were　investigated　experimentally.　As　compared　to　the　previous　study　irradiated　by　a　nanosecond　pulsed　laser,　such　factors　as　melting,　ablation　and　crystallization　thresholds　dropped　remarkably　by　a　picosecond　laser　irradiation,　and　with　the　increase　of　Sn　content　those　factors　were　further　decreased.　Due　to　the　replacement　of　Ge　atoms　by　Sn　atoms,　the　Sn　incorporation　expanded　the　lattice　constant　so　as　to　introduce　the　mechanical　stress　which,　together　with　the　thermal　stress　generated　after　laser　irradiation,　significantly　affected　the　atomic　movement　during　the　crystallization　process.　High-resolution　transmission　electron　microscopy　(HRTEM)　observations　showed　that　GST　with　a　lower　Sn　content　of　10%　tended　to　form　sub-grain　boundaries　by　local　atomic　shear　to　ensure　long-range　ordering　of　crystals,　but　with　the　increase　of　the　Sn　doping　to　30%,　the　long-range　ordering　structure　was　broken,　instead　of　some　atoms　arranged　randomly,　which　were　mainly　Ge　atoms,　separating　out　from　the　lattice　because　of　the　replacement　by　Sn　atoms.　These　extra　Ge　atoms　were　not　involved　in　the　crystallization　process,　proved　by　the　Raman　spectroscopy.　The　present　study　is　fundamental　for　the　design　of　advanced　storage　device　based　on　PCMs.