Different　pulse-shaping　mechanisms　were　investigated　experimentally　and　numerically　in　passively　mode-locked　thulium-doped　fiber　lasers.　Conventional　solitons　were　demonstrated　in　a　passively　semiconductor　saturable　absorber　mirror　mode-locked　anomalous　dispersion　thulium-doped　fiber　laser.　With　normal　dispersion　fiber　and　spectral　filter　added　in　cavity,　pulse-shaping　processes　were　theoretically　analyzed　in　the　presence　of　dispersion　map　and　dissipation　in　thulium-doped　fiber　lasers.　The　existence　of　parabolic　pulse　as　nonlinear　attraction　was　proved　and　distinct　pulse　intensity　profiles　evolution　from　Gaussian　shape　to　parabolic　shape　was　proposed　in　dissipative　dispersion-managed　thulium-doped　fiber　lasers.　(C)　2015　Optical　Society　of　America