在可控源电磁场三维有限差分数值模拟过程中，低频时数值模拟的收敛速度变慢，导致获得精确结果的时间变长。引入电流密度的散度校正方法可以加快低频数值模拟时的收敛速度，提高解的精确性。笔者在研究可控源电磁场三维有限差分数值模拟算法的基础上，利用电流密度的散度为零，推导了散度校正公式并利用迭代解法实现了散度校正算法。模型试验表明，在低频时，散度校正能大幅度提高三维电磁场数值模拟的速度和精度，异常体规模越大，数值模拟的频率越低，散度校正的效果越明显。

In the 3D numerical modeling of controlled source electromagnetic fields，the convergence rate of numerical simulation became slower in extremely low frequency，which led to the time for getting precisive results became longer． Therefore，the application of divergence correction of electric current density at low frequencies has been introduced to help the case improved． Based on the study of 3D controlled source electromagnetic staggered grid finite difference algorithms，the authors derived divergence correction formula by using the current density of the divergence condition as zero and implemented divergence correction algorithm with iterative method． Model tests showed that divergence correction can reduce the time and improve accuracy effectively in the low frequency range， and the effects were more obvious with larger- scale anomalies and lower frequencies．