Low-frequency magnetic shielding is usually made with finite-size metallic plates. The discontinuity on the shield is unavoidable, and degrades the performance of shielding. In this paper an equivalent circuit method was proposed to model the joint of conductive plates, and to evaluate the magnetic fields around the joint. The circuit equation using total cell current was presented. The modeling method was validated experimentally. Shielding performance of a shield against various joint parameters was also investigated. It is found that reasonable shielding performance can be achieved if the joint is provided with an adequate mating surface area and multiple fixing points.