In this work, we study the nonreciprocal TE-TM mode conversion phenomenon, by the simulation of magneto photonic crystal fibre (MPCF). This MPCF consists of a periodic triangular lattice of air-holes filled with magnetic fluid (Fe 3 O 4 ) into a Terbium Gallium Garnet (TGG) fibre. It is well known that, owing to its excellent transparency properties and its resistant character to laser damage, TGG is always selected as a Faraday rotator material. Also, TGG has a high Verdet constant related with the Faraday rotation (FR) effect. Here, with the consideration of the effect of gyrotropy, our simulations are associated with some calculations of the FR and modal birefringence. In this MPCF, the light is guided by internal total reflection, like classical fibres. However, it was shown that the designed MPCF could function as a mode converter with much stronger conversion efficiency than those of the conventional fibres.