In this paper, a kind of magnetic photonic crystal fiber of Yttrium iron garnet (YIG) is presented. The influence of gyrotropy on TE-TM mode conversion is analysed, which depends on Faraday rotation. The structure parameters are simulated and optimized. The optimum efficiency of 93.57% is obtained. Faraday rotation and modal birefringence have been calculated by varying gyrotropy from 0.01 to 0.04. The numerical results reveal an increased Faraday rotation and a reduced modal birefringence of 10-5. The enhanced properties of the structure could improve photonic devices performance, which make it suitable for magneto-optical isolators.