This paper investigates the changing rules and sensitivity of the external excitation oscillator when the parameters and time-varying modality of the external excitation stream changes. The numerical simulation and experiment are employed to investigate the changes of stimulation ability and retention ratio of total pressure K of oscillation jet flow. The results show that K decreases when the total pressure of external excitation steam drops. The leaking excitation stream on the non-excitation side also makes K slightly down and significantly reduces the excitation power. The retention ratio of the total pressure K is observably reduced when the duty ratio decreases due to the early shut-off of the excitation stream. The gradual advance of initial pressure of excitation stream has little effect on K, but loss or gradual decline of the pressure during the middle and later periods markedly decreases K. The studies show that external excitation oscillator adapts better to the changes of excitation stream parameters. When the parameters fluctuate less than 20%, the performance of the oscillation can still maintain higher retention ratio of total pressure K. The lower limit of K is 10% higher than that of the existing self-excitation oscillator. The study provides the basis and reference for effective application of the oscillator.