It is concluded that there is weaknesses in electromagnetic theory according to experiment result of static electric field exists around permanent magnet, and weaknesses and problems for electromagnetic theory are analyzed from 14 aspects. It indicated a basic weakness in electromagnetics that it failed to explain internal cause for surface phenomena including electromagnetic induction, displacement current and Lorentz force. It is deduced that electric field movement is the fundamental factor of all electromagnetic phenomenon. Through analysis on electric field, it is illustrated that the internal cause and physical process of all electromagnetic phenomenon. It is deduced that magnetism comes from natural law that light speed is constant and realistic light speed is the ideal one.