We report a tungsten diselenide () polyvinyl alcohol (PVA)-based, saturable absorber and related experiment results of a Q-switched fiber laser. -PVA film is synthesized by liquid phase exfoliation method, and its saturable absorption is measured via a nonlinear transmission experiment. The result shows that -PVA saturable absorber has a modulation depth of 3.5%, which means it has potential for generating an ultrafast pulse laser. We apply this absorber into a ring-cavity erbium-doped fiber laser and obtain Q-switched pulses under appropriate pump power. Our work demonstrates the reliable nonlinear optical characteristics of and the feasibility for this two-dimensional material to be applied in the field of nonlinear optics.