On the basis of Vlasov equation, we extend the results of our previous work [10] and obtain the general coupling equations for the electrons, ions of plasmas and the electromagnetic radiation. We have solved these coupling equations, and obtaind the threshold powers and growth rates of the stimulated scattering and harmonic radiation. Finally, we propose a successive generating mechanism of the harmanics and sub-harmonics, such a mechanism is in agreement with the experimental results in the literatures.