The electronic oxygen regulator (EOR) is a new type of aviation oxygen equipment which uses electronic servo control technology to control breathing gas pressure. In this paper, the control method of EOR was studied, and the dynamic model of the aviation oxygen system was established. A disturbance-observer-based controller (DOBC) was designed by the backstepping method to achieve the goal of stable and fast breath pressure control. The sensitivity function was proposed to describe the effect of inspiratory flow on breath pressure. Combined with the frequency domain analysis of the input sensitivity function, the parameters of the DOBC were analyzed and designed. Simulation and experiment studies were carried out to examine the control performance of DOBC in respiratory resistance and positive pressurization process under the influence of noise and time delay in the discrete electronic control system, which could meet the aviation physiology requirements. The research results not only verified the rationality of the application of DOBC in the breath control of EOR, but also proved the effectiveness of the control parameters design method according to the frequency domain analysis, which provided an important design basis for the subsequent study of EOR.