Dither control is an important factor for the performance of dither ring laser gyro (DRLG). The decoupling method of DRLG dither control system is studied based on gyro oscillation characteristics. It is studied that the phase feedback is a good selection to trace resonant dither frequency. On tracing resonant frequency, as well as changing amplitude of dither drive signal on the zero-position-point, the dither amplitude responses can be simplified as a 1-order system, and the dither-amplitude-control is independent to frequency-tracing to realize the decoupling control，which improves the control performance of DRLG dither control system.