A detailed investigation about the two methods of kinetic theory of ECRM is given in this paper. One of them based on integration in the waveguide coordinate system was presented by the scientists of NRL of America

and the other based on the local field expansion in the electron guiding center coordinate system was proposed by the author of the present paper. After detailed analysis and comparison with these two methods

the paper points out that the later one has some advantages over the first one; it approaches more simply and directly

and has more explicit physical meaning. Furthermore

it makes the electron equilibrium distribution functions simpler.