Bismuthene, as a new two-dimensional (2D) material made up of diazo metal elements, has drawn massive attention for its unique electronic, mechanical, quantum, and nonlinear optical properties. In recent years, researchers have increasingly turned their attention to the ultrafast photonics fields based on bismuthene. However, the internal ultrashort pulse dynamics has seldom been explored yet. In this work, the nonlinear optical properties of bismuthene nanosheets have been studied and applied in a passively mode-locked fiber laser. The saturation intensity and modulation depth of SA device are about 2.4 MW/cm2 and 1%, respectively. Thanks to the narrow bandgap of bismuthene and tapered fiber structure, a special kind of noise-like multipulses have been obtained. The evolution of the pulsed laser is also studied. This proposed pulsed fiber laser based on bismuthene SA device is well suitable for some applications such as material processing, optical logics etc.