The invention provides a polarization imaging principle-based polarization maintaining fiber axis alignment device and an axis alignment method. The device comprises an upper fiber limiting plate and a lower fiber limiting plate, wherein one side of the upper fiber limiting plate and one side of the lower fiber limiting plate are connected through a cylindrical shaft; circular holes are formed in the upper and lower fiber limiting plates; semicircular grooves penetrating through the circular holes are formed in the upper and lower fiber limiting plates; the diameters of the semicircular grooves in the upper and lower fiber limiting plates are equal. A polarization maintaining fiber is placed on the axis alignment device. A polarization microscope is turned on, a focal length of the microscope is adjusted to enable the polarization maintaining fiber to present a polarization interference image of an inner cladding and a fiber core on the microscope, and a distinct image is acquired by virtue of a CCD (charge coupled device) camera. The polarization maintaining fiber is rotated to obtain characteristic images of an internal structure of the polarization maintaining fiber under different azimuths, and a characteristic curve is established through a corresponding relationship between a characteristic value and a rotating azimuth, thereby implementing axis alignment of the polarization maintaining fiber. The device for axis alignment of the polarization maintaining fiber has the advantages of high axis alignment speed, high accuracy and applicability to polarization maintaining fibers of different types.