An　all-normal-dispersion　WS2　mode-locked　Yb-doped　fiber　laser　was　demonstrated.　The　saturable　absorber　(　SA)　is　a　piece　of　WS2-PVA　film　which　is　sandwiched　between　two　fiber　connectors.　The　modulation　depth　and　saturation　intensity　of　the　WS2-PVA　film　were　1.78%　and　81　MW/cm(2),　respectively.　When　the　WS2-PVA　film　was　utilized　in　the　laser　cavity,　stable　mode　locking　occurred　with　the　pump　power　of　140　mW.　The　maximum　single　pulse　energy　was　estimated　to　be　more　than　2.82　nJ.　Besides,　in　order　to　know　more　about　the　influence　of　the　SA　on　the　generation　of　ultrashort　pulses,　the　dynamic　evolution　of　mode-locked　lasers　with　the　parameters　of　SAs　was　studied　by　solving　the　Ginzburg-Landau　equation.　Thus　the　high　pulse　energy　could　be　reached.