1. College of Geo- exploration Science and Technology，Jilin University，Changchun 130026，China; 2. Tianjin Center，China Geological Survey，Tianjin 300170，China

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．