In this peper, the theoratical calculation of electric parameters forelectric fish screen (EFS) of divider-type is presented acoording to the principles ofequivalent circuit, axis-mirror image method and electromagnetics respectively. Theirconstraint conditions of simplification and approximation are also analyzed. The analy-sis shows that the theoratical calculation formula are applicable to different situation,that is, (1) the equivalent circuit method is approximately suitable to comparativelylarge aquatic areas, in deepwater layers or center part of the blocking section (calledsituation 1); (2) the axis-mirror image method is accurately suitable to the mirror planeperpendicular or parallel to the line of the electrode absolutely (called situation 2), otherwise, it is mistaken and senseless; (3) the electromagnetics method is accuratelyuseful to situation 1. The calculated examples show that: (1) The error between the equivalent circuit method and the electromagneticsmethod is less than 5%, and in other words, the error can be neglected in engineeringdesign and analysis. (2) The error between the electromagnetics method and the axis-mirror imagemethod is significant when the electrode line is close to the image plane, and unsigni-ficant when the distance from the electrode line to the image plane is larger than 5d. In practice, the EFS of divider-type is usually designed and located on the spillwayof reservoir. The dam and the bank of spillway are certainly angular to the electrodeline in oder to improve the efficiency of stopping fish escaping. The electric parametersare thus calculated by both the equivalent circuit method and the electromagneticsmethod, but the axis-mirror image method.