The invention discloses a control method and 
system for realizing polarization stability, and belongs to the technical field of 
optical fiber communication and 
optical fiber sensing. According to thecontrol method and 
system of the invention, the output light polarization state of any input light polarization state after passing through a 
polarization controller is rapidly adjusted to be close toany specified target polarization state on a 
Poincare sphere through a rapid positioning 
algorithm, and then the output light polarization state is further stabilized to a target polarization state through a random 
gradient descent algorithm. Therefore, any polarization state can be stabilized to any set target polarization state. The specific implementation 
system is composed of an input end polarization analyzer, an output end polarization analyzer, a calibrated 
polarization controller, a single-
chip microcomputer and the like; the input polarization analyzer and the polarization controllerwith the calibrated 
phase difference and 
voltage relation are used for rapid positioning, and meanwhile, the output polarization analyzer is combined with the 
stochastic gradient descent algorithm tofinally stabilize the output polarization state to a set value. According to the polarization stability control method, the searching speed and the local extreme value avoidance are balanced, and thepolarization state can be rapidly and stably changed to any designated target polarization state.