从毕奥-萨伐尔的基本定律出发，引入有效半径、有效空间位置和有效空间取向等概念，通过比较电流环和磁偶极场的远场近似计算与严格的带电螺线管磁场的计算结果，采用优化螺线管结构和构建计算模型，可以有效地克服螺线管本身带来的空间磁场有限长度效应. 在有效空间范围内进行数值模拟的结果表明，磁偶极场的远场近似不仅可以满足磁场计算的精度要求，而且具有极高的计算速度. 可以实时地实现具有多带电螺线管复杂结构的电磁计算，满足电磁空间定位和电磁导 　　航的要求.

Based on the Boit-Savart law，the concepts of effective radius，effective spatial location and effective spatial orientation are introduced by comparing the far-field approximate calculation of charged current loops and the dipole magnetic field with the strict calculation of the magnetic field of the solenoids. By optimizing the solenoid structure and rebuilding，the computing model can overcome the limited length effect of the spatial magnetic field brought by the solenoid itself effectively. By simulating the system within the effective region，the result shows that the far-field approximate calculation of the dipole magnetic field not only meets the accuracy in magnetic field calculation but also has very fast calculation speed. The method can realize the magnetic calculation with the complex structure from many solenoids in real time and satisfy the real-time requirement of spatial positioning and electromagnetic navigation.