Abstract: The chaotic planar motion of a magnetic rigid satellite in a circular orbit nearthe equatorial plane of the earth is investigated in the present paper. The existenceof chaotic motion of the satellite is predicted by using Melnikov's method and verified by numerical computation in conjunction with the Poincare map. It is shownthat the periodic disturbance of the magnetic field of the earth can cause chaoticmotion of the satellite and the increase of the disturbance can intensify the chaoticmotion.