In this paper, we have studied theoretically the resonant Self-focusing of two-frequency laser beams in plasmas. From the plasma fluid equations, we have derived the expression of the nonlinear dieletric contants of plasmas driven by two-frequency laser beams and showed the effect of the ponderomotive force of the plasma waves. After giving the approximate solution of longitudinal electrostatic field, the characters of resonant Self-focusing are showed. Finally, the influence of resonant Self-focusing on particle aooeleration in beat wave accelerator also be discussed.