Magnetic resonance weak force microscopy (MRWFM) can achieve non-destructive high-precision structural information detection of substances. This advantage makes MRWFM be widely applied in fields of physics, biology, medicine, and so on. The super-sensitive cantilever beam is one of core composition to realize weak force detection in this technology. In recent years, two-dimensional nanomaterials have attracted more and more attention due to their unique physical properties. In order to achieve the detection of the magnetism of two-dimensional nanomaterials, the design of double-arm micro-cantilever beams with differential amplification based on single arm micro-cantilever beam model was proposed. Then the magnetic field distributions inside and outside of the scan balls fastened on the double-arm micro-cantilever beams were analyzed. Finally, the numerical simulation of the cantilever beam was completed, taking the single-crystal silicon cantilever beams and CoSm magnetic ball probe as examples. It is found that the scheme can improve detection sensitivity of cantilever beam significantly.