Metal nanomaterials possess excellent physical properties, which can be used as catalysts, storage carriers, and nonlinear photonic devices. Nickel nanoparticles have become increasingly crucial for ultrafast applications due to their broadband saturable absorption properties. Herein, nickel nanoparticles are prepared through an oil-phase method, followed by integration with nitrocellulose to form a composite film. Microscopic images, linear transmission, and nonlinear absorption properties of the film are presented to investigate the characteristics of nickel nanoparticles. Furthermore, Yb-, Er-, and Tm-doped fiber lasers are built based on a nickel-based saturable absorber, where Q-switched pulses are realized at 1, 1.5, and 2 μm. These results prove that nickel nanoparticles exhibit broad-band saturable absorption, showing promise for facilitating highperformance pulsed lasers.