Abstract: Up to now, the empirical formula is usually used to design the permanent magnet design. Because of the nonlinear characteric of the material, the design formula is difficult to correct; it is only a simplified approximation. The error may be great, which will cause heavy economical less, if expensive permanent materials, such as the rare earth permanent material, are used. This paper describes the result of the numerical calculation method for such a problem. This method can select the optimum working condition, and by making a reasonable compromise, good performance can be got at a lower cost. The authors calculated a magnetic circuit used for a moving-coil meter and obtained results which agree with the measured values.