We　demonstrated　an　all-fiber　passively　mode-locked　980　nm　picosecond　laser　using　KP15　materials　as　saturable　absorbers　(SAs).　The　micron-sized　wire-like　KP15　crystals　were　prepared　using　a　vapor-phase　transfer　method.　The　material　not　only　shows　excellent　optoelectronic　properties,　such　as　optical　anisotropic　and　large　binding　energy,　but　also　long-term　stability.　By　inserting　the　KP15　crystals　into　the　ytterbium-doped　all-fiber　laser　cavity,　a　mode-locked　980　nm　laser　with　a　pulse　duration　of　30　ps,　a　repetition　rate　of　15.65　MHz　and　spectral　width　of　5.6　nm　was　achieved　for　the　first　time,　to　the　best　of　our　knowledge.　In　addition,　we　investigated　the　long-term　stability　of　the　KP15-based　mode-locked　980　nm　laser,　and　the　root-mean-square　of　the　output　power　of　the　picosecond　pulse　was　only　1.03%　when　operating　for　4　h.　The　results　indicated　that　the　KP15　material　prepared　using　a　chemical　vapor　transport　method　was　a　promising　SA　for　ultrafast　fiber　laser　generation.