Abstract: Because stress concentration maybe leads to safety accidents during the use of ferromagnetic material components, a U-shaped probe of magnetic stress sensor was designed and the finite element analysis based on COMSOL MULTIPHYSICS was performed. The design uses a U-shaped probe as a sensor to form a closed loop with the tested steel plate, transforming magnetic signals into electrical signal outputs. A model for 3D finite element analysis on the sensor was established based on COMSOL software and the main influence parameters were simulated. The optimal parameters were selected based on the simulation results, and this provides the theoretical basis for the design of hardware. Finally, the hardware is produced.