The cutoff-wavelength measuring methods of polarization-maintaining optical fiber (PMOF) has been investigated and the implement method has been presented.The established the cutoff-wavelength measuring device for the PMOF has realized the measurements of the fast- and slow-axis cutoff wavelength for some kinds of PMOF,? respectively, By the validation experiment,?The principle factors which influence the cutoff-wavelength measuring results have been analyzed. The built measuring system has certain significance on the relevant tests operated by those who study and manufacture the PMOF.