In this paper, a dynamic model is provided to obtain the waveform of the unbalanced magnetic force in the cage rotor induction machines with static eccentricity. The provided dynamic model is based on the voltage state-space equations of the coupled circuits in the eccentric induction machine. In the model, each rotor loop is considered as a separate circuit. To avoid computation of the air gap flux density and evade of magnetic pressure integration in each time-step of Runge-Kutta computations and consequently reducing the computation time of dynamic simulations, a static function of the stator and rotor bars' currents are proposed for computation of the unbalanced magnetic force. The parameter of the proposed function is obtained by analyzing the air gap field density. Finally, the waveform of the unbalanced magnetic force of the eccentric induction machine is obtained in different load conditions.