Based on the basic principle of electromagnetism，we discuss the distribution of magnetic field of the mirror constructed by two parallel current carrying rings，as well the relationship of magnetic flux conservation for the moving particle in uniform magnetic field. The gravity drift motion of particle in weak inhomogeneous magnetic mirror field is studied by using theoretical analysis and numerical method. Our results consist with the formula of gravity drift in magnetic field，which show that the existence of gravity violates the conservation of magnetic flux in weak magnetic field.