According to the coupledmode method, the propagation of guided optical waves in spun magnetooptic fibers (SMOFs) was investigated by considering the coupling of linear birefringence, fiber spun and the magnetooptic (MO) effect. The results show that, 1) the SMOF′s eigen optical waves are of constant ellipticity along the SMOF; 2) from the viewpoint of input/output properties, the SMOF may be regarded as a linearly birefringent MO fiber (LBMOF) followed by a polarization rotator, in which the LBMOF has the same length as the SMOF and its MO coupling coefficient is equal to that of the SMOF minus fiber rotation ratio. The polarization characteristics of the SMOF under magnetic control were analyzed as well. For the case of incident linear polarization, the ellipticity and azimuth of light output from the SMOF can be linearly adjusted by changing the MO coupling coefficient or magnetic field, which is helpful for the design of magnetically tunable polarization controllers.