By using a fiber grating as a reflector, a small part of the dual-polarization fiber laser is delayed by the fiber delay line, and then fed back to the laser cavity, which can reduce the phase noise of beat frequency. Results show that the longer the feedback time is, the greater the noise reduction magnitude is. With a 50 m single mode fiber as the delay line, more than 20 dB phase noise reduction is achieved for a dual-polarization fiber grating laser, and a phase noise of -92 dBc/Hz at 10 kHz offset is achieved. The polarization state of optical feedback has influences on noise suppression capability of the external optical feedback system, and it has weak tuning capability to beat frequency of the dual-polarization fiber.