将光纤中磁光效应和非线性效应作为微扰，推导了磁光四波混频的耦合模方程.通过解析解研究了各向同性磁光非线性光纤的参量过程，并指出利用磁光耦合系数的色散特性可以实现四波混频的相位匹配.同时，采用龙格-库塔法分析了在线双折射磁光非线性光纤中，忽略费尔德常量的波长依赖性时，左旋圆偏振光参量增益的磁控特性，指出了实验中采用较高费尔德常量的非线性光纤的必要性.研究表明：1)对于低线双折射磁光非线性光纤，优化双折射大小可以获得最大的参量增益；2)根据参量增益对磁光耦合系数的单调依赖特性，适当选择光纤长度、泵浦功率以及输入导波光的偏振态，可使参量增益的磁可调范围大大提高.

The coupled-mode equation for the magneto-optic four-wave mixing existing in a fiber with magneto-optic and nonlinear effects as perturbation is derived. The parametric processes of the isotropic magneto-optical nonlinear fiber are analytically investigated, and the phase matching condition can be achieved by the dispersion characteristics for the magneto-optic coupling coefficient. In the case that the wavelength dependency of fiber Verdet constant is negligible, the magnetic control characteristics of fiber parametric gain are analyzed for the incident left-hand circular polarization. The necessity of using magneto-optic and nonlinear fiber with high Verdet constant in the experiments is pointed out. The results show that, 1) for the magneto-optical nonlinear fiber with low birefringence, the maximal parametric gain can be obtained by optimizing the magnitude of fiber birefringence; 2) from the monotonic dependence of parametric gain on the magneto-optic coupling coefficient, the magnetic adjustability of parametric gain can be improved by appropriately choosing fiber length, pump power and polarization states of guided optical waves.