The working process of inlet under the condition of different given influencing factors in the inlet/combustor/nozzle integrated flow field was discussed. The effect of fluctuation of nozzle diameter on the inlet was investigated. We also explored the effect of time and space fluctuation of inlet exit pressure on the inlet. The operating characteristics of inlet with different interfering factors were achieved. The result showed that time fluctuation of inlet exit pressure can bring the non-uniform distribution of inlet exit pressure. The response time of space fluctuation was longer than the that of time fluctuation. The recirculation zone at the diffusers moved upward gradually when the nozzle diameter was reduced.