Numerical simulations and experiments were conducted to analyze the dynamic characteristics of a newly developed bellows-type stabilizer, which maintains a steady propellant mixture ratio in the gas generator of a liquid rocket engine. A nonlinear mathematical model of the stabilizer and a linear version of the model were developed. The dynamic characteristics predicted by the linear model showed good agreement with experimental results, thus proving the validity of the model. It was found through sensitivity analyses that the main design parameters affecting the dynamic characteristics of the stabilizer system are the orifice diameter and the length of the pilot line.