He-Ne gas ring lasers are the core device of laser gyros. In order to avoid the competition effect of the modes operating in the same and reverse directions with rotation in a ring laser, the laser gyro at the single longitudinal mode needs to adjust the composition of Ne isotopes in the gain medium and adopt a dual-isotope gain medium. For this purpose, the Lamb theory and plasma dispersion function were used to study the effects of the frequency splitting of Ne isotopes, isotope composition, inflation pressure, and other factors on the intensity tuning curves of a ring laser. Besides, the experimental platform for the line-type detection of the intensity tuning curves in the laser gyro was set up. At the Ne ²⁰/Ne ²² ratios of 1∶1 and 7∶3 and the inflation pressure of 400 Pa, the intensity tuning curves of the laser gyro were detected, verifying the correctness of the theoretical analysis. In conclusion, this study lays a foundation for the frequency stabilization of laser gyros at the asymmetrical position of frequency with double longitudinal modes.