In order to solve the problem that the frequency stabilization system with light intensity comparison is subject to the parameters of optoelectronic components, a frequency stabilization circuit with small dithering was designed for nonplanar four-mode differential laser gyro. The beat wave amplitude in clockwise (or anticlockwise) light of four-mode differential laser gyro was amplified and detected, and then sampled to a digital signal processor (DSP) via analog to digital converter. Small dithering method could be used to stabilize the frequency of four-mode differential laser gyro under the condition that the beat wave amplitude reaches maximum when the gyro operates steadily. A digital system for frequency stabilization was designed with the DSP. Precision of frequency stabilization was 2×10-9 for 1 s sampling. What′s more important is that frequency stabilization point was immune to variations of parameters of optoelectronic components. The frequency stabilization circuit is precise and universal, so it is of some significance to improvement of capability over severe environment of four-mode differential laser gyro.