By making use of the method of quantum field theory, the A.C. magnetoresistance, the Hall effect, and the cyclotron resonance phenomena in electron-phonon system are investigated. The relaxation times and effective masses, which depend on the frequency of external electric field ω and intensity of static magnetic field H, and the strict expression for the line shape of cyclotron resonance are obtained in this way. In our work, the effect of Coulumb interaction between electrons, the effect of quantization of orbital motion, and the influence of alternating electric field have been taken into account.