The invention belongs to a method and a device for transforming and stabilizing an optional polarization state. The method and the device adopt incident light of the optional polarization state, and the polarization state is changed after the incident light passes through a polarization controller; a polarization detector monitors the changed polarization state and transmits the result to a data processing unit; and the data processing unit adopts a PSO arithmetic to search and track an object polarization state to be output and feeds back the polarization state to the polarization controller so as to realize the conversion and stable control on the polarization state of an incident optical signal. The method and the device can convert the optional polarization state of an input optical signal into the needed object polarization state, realize on-line tracking and stabilize the polarization state of the input optical signal onto the object polarization state. The method and the device have the advantages of feasible application and wide prospect.