An optical polarization independence reflection structure applies to fine tracking mirror in satellite-based quantum key distribution is proposed. This structure is composed of magneto-optical crystal and two same mirrors. The results of simulation show that single mirror badly influences the polarization state. For the mirror with refractive index 1.52, the quantum bit error rate caused by mirror is 40%. The quantum bit error rate caused by polarization independence reflection structure is not more than 0.25%, particularly, it is approaching zero when the deflection is approaching zero.