This paper presents a novel laser feedback interferometer for metrology of large range displacement. A Birefringence-Zeeman dual frequency laser is applied in the system. Due to its strong optical feedback effects, the intensity modulation curves of the two polarized lights will have a zero intensity part in a period. A quartz crystal is used in the external feedback cavity as a birefringent element. And a phase difference between the two lights can be adjusted to π/2. Thus, the intensity modulation curves in a period can be divided into four polarization zones with equal width. When the displacement of the object to be measured is produced, the four polarization zones will appear in sequence. According to the appearance order of the four zones, the direction of the displacement can be discriminated without ambiguity and the resolution of the system can be greatly increased. It is confirmed that the laser feedback interferometer has a resolution of 79.1nm and with a linearity of 0.01% over the whole measurement range of 15mm.