The influence of the polarization feedback of the fiber ring on the dynamics of the isotropic semiconductor optical amplifier (SOA)-based fiber ring system is studied by theoretical simulation and experiment. It is found from simulation that a bistable orthogonal-polarization light under stationary can be realized by a polarization feedback of a 90°-rotation, and a dynamically-depolarized polarization chaos under non-stationary can be realized by properly setting polarization feedback. Experimentally, such a orthogonal-polarization modulation light is observed and a dynamically-depolarized polarization chaos with dynamical degree of polarization less than 1% is obtained in a SOA fiber ring system. The experimental results are well consistent with the theoretical simulations.