For the dead zones phenomenon of longitudinal modes modulating signal in the total reflection prism laser gyros (TRPLG) during in single longitudinal mode frequency stabilization, a novel technique for the double longitudinal mode frequency stabilization of the TRPLG is studied. By analysing the theory of power tuning curve, amplitude and phase characteristics of the small jitter modulation signal in double longitudinal mode are derived. The double longitudinal mode frequency stabilization scheme is proposed, and the control system for the double longitudinal mode frequency stabilization of the TRPLG is built by software and hardware circuit design. In the fixed and varied temperature environments, the experimental tests for the single longitudinal mode and double longitudinal mode frequency stabilization are conducted. The results show that, comparing with the control method for single longitudinal mode frequency stabilization, the frequency stabilization accuracy of the double longitudinal mode can be improved by over 60%, and the accuracy of gyros is also increased accordingly.