Polarization controller (PC) is an important device for the automatic polarization control algorithm, which is also an important part in the quantum key distribution system. A new method of analyzing the polar blind zone of the fiber squeezer polarization controller is presented based on the relation between the phase of the fiber squeezer and the rotation axis of the polarization state trajectory. The control principle is analyzed theoretically, and the interaction law between the changed phase and the rotation axis of the state of polarization′s trajectory is deduced. Based on the above results, the “polar blind zone” phenomenon of the two fiber squeezers cascade polarization controller is further expounded, namely only in the extremely individual input polarization state, arbitrary polarization states can be output. The vast majority of the input polarization states cannot arrive certain areas in the Poincare sphere. The accuracy of theoretical analysis is verified through comparing simulation results and experimental results. An idea of the polarization control algorithm based on avoiding blind area is proposed, which can reduce variable degrees of freedom.