The fatigue behavior of a microcantilever beam loaded by various magnetic force's is investigated. The MEMS fabrication techniques, such as exposure, lithography, etching.. etc.. are applied to construct the micro structures on a silicon wafer. FEM and SEM are employed to study the relations between fractographies, stresses, and strains. The experimental results indicate that the deformation, stress and strain increase as the magnetic force increases. while the fatigue cycle time decreases with the load. The fatigue life lies in the range of 1-5 x 10(7) cycles at 12-15 MPa produced by the magnetic flux. Fracture occurs at the location of the maximum stress as predicted by an analytical approach. (C) 2004 American Vacuum Society.