A wideband waveguide electro-optical modulator (EOM) is driven by multiple frequencies signal. By synthesizing three frequencies and using these frequencies to drive the wideband waveguide EOM, three pairs of sidebands are added to the carrier laser frequency. Three sidebands on one single side of the carrier are used to laser frequency stabilization by Pound-Drever-Hall (PDH) technique. By adjusting the phase of one frequency signal, the baseline drift of the PDH error signal is controlled. The residual amplitude modulation (RAM) noise in frequency locking system also causes error signal baseline drift, through active phase modulation frequency signal feedback control system, the residual amplitude modulation noise suppression is realized. Experimental results show that after applying the active closed loop feedback system, the RAM noise is suppressed over 30dB, and noise drift is suppressed effectively.