By adjusting the Mn concentration,we systematically investigated the magnetic properties,especially the exchange bias field(Hex),in Ni81Fe19/Ni100-xMnx bilayers.In the range of 534≤x≤600,the largest exchange bias field(～175kA/m)was achieved,and at the same time the reduction of magnetic moment due to the Mn diffusion into the Ni81Fe19 layer was lower than 20%.High-angle x-ray diffraction(XRD)showed a variation of Ni１００-xMnx lattice parameters when altering the Mn content:the more the Mn content,the larger the lattice parameters.It was found that the as-deposited Ni100-xMnx films with their lattice parameters close to those of θ-phase of NiMn alloy could be transformed into θ-phase relatively easily.Finally, the exchange bias of the bilayers with different Ni100-xMnx thicknesses was studied.We first obtain a 80 kA/m exchange bias field in the Ni81Fe19(150nm)/Ni100-xMnx(90nm)bilayers when Mn content increases to 706% after annealed at 240℃ for 5h,while the magnetic moment of the ferromagnetic layer was nearly umchanged.