Abstract: In Raman-type cesium atom interferometer, two laser beams at 852 nm with stable relative optical power and frequency difference of 9.193 GHz are required for Raman beam. Raman beam is usually generated by modulating the master laser using an electro-optic modulator. However, the sideband-to-carrier ratio of Raman beam is sensitive to temperature and humidity, which degrades long-term stability of atom interferometer through the light shift effect. A servo-control technique for stabilizing the sideband-to-carrier ratio of Raman beam is proposed in this paper. We beat the Raman beam with a reference beam, and then monitor the beat note signals at each frequency points using a frequency spectrum analyzer and calculate the sideband-to-carrier ratio. Then feedback is applied to the driving signal of the electro-optic modulator to achieve active stabilization. Eventually, we demonstrate a long-term stability of the sideband-to-carrier ratio of 1×10^-5 V/V@20 000 s. The stability of the central frequency of Raman spectrum is enhanced by roughly threefold relative to the free-running mode. This study provides a reliable foundation of enhancing the stability of Raman-type cesium atom interferometers.