The invention discloses a double-polarization-state optical-fiber vibration sensing time domain detection system. The system performs the following steps: light splitting is performed on a sensing optical signal to generate a first light beam and a second light beam; a current light power value of the first light beam is detected; the second light beam is input into a double-polarization-state polarization analyzer, and then is output to be a first polarization light beam and a second polarization light beam; a polarization light power value of a third polarization light beam and a polarization light power value of the second polarization light beam are detected, and a deviation absolute value set of the polarization light power values of the third and second polarization light beams; a double-polarization-state energy absolute value set is generated; a relative energy value is calculated according to the current light power value of the first light beam and the double-polarization-state energy absolute value set; and whether an optical-fiber vibration exists is determined according to the relative energy value and a preset relative energy threshold. The system can achieve detection of the optical-fiber vibration without adding a polarization controller and using a polarization maintaining optical fiber in a cost-limited optical-fiber polarization state vibration sensing system.