In this study, the influence of the gas pressure ratio of helium to neon on the characteristics of a ring laser gyro is investigated. The relation between the power tuning curve and the gas pressure ratio in a ring laser cavity is theoretically derived from the plasma dispersion function. A specific type of a ring laser gyro is used for experimental measurements. An inflatable experimental device with strong operability,adjustable gas pressure ratio, and real-time monitoring of the gas parameters is presented. The relation between the output gain of the laser gyro and gas pressure ratio is determined. The optimal working gas pressure ratio of helium to neon is also determined. Experimental results indicate a positive relation between the laser output gain and gas pressure within a certain range. The output gain reaches its maximum at a certain pressure value and then falls with an increase of the pressure to the point, where the laser output becomes zero.