In the field of precision measurement and aerospace, the Magnetic-grating-like displacement sensor [1] has high requirements on the uniformity of magnetic field generated by permanent magnet, while the magnetic field uniformity of common rectangular permanent magnet is poor, which affects the high precision and reliable measurement of hydraulic cylinder displacement, and is difficult to meet the application requirements. Therefore, this paper designed a curved permanent magnet with a unique structure, First based on the molecular current hypothesis and the Biot-Savart Law, To derive the expression of the magnetic induction intensity of a curved permanent magnet at any point in space; Then, the structure size of the permanent magnet was optimized using the Maxwell electromagnetic field analysis software, Determine the basic size of the curved permanent magnet; Finally, the experimental platform was set up to measure the magnetic induction intensity at the corresponding position of the permanent magnet, By comparing the measured data with the Maxwell simulation data, The results show that the simulation and experimental results are basically consistent, And the maximum relative error in the uniform region of the magnetic field does not exceed 3%, The feasibility of the construct was verified.