In order to meet the requirement of impulse pressure measurement and calibration in aerospace field, a generation method of medium and low gas impulse pressure was developed, which was based on the mode of outlet modulation, and the medium and low gas impulse pressure can be produced in the fixed cavity by motor motion.. Through the precision control of motor, the small impulse pressure was produced in the fixed cavity by motor motion. According to the motion state of the rotary valve and the change of the flow area of the valve port, the gas pressure relation was established. The feasibility of producing the gas impulse pressure by the rotary valve was verified by the simulation results. The experimental results showed that the impulse pressure amplitude was below 4 MPa and the impulse width was less than 15 ms. The influence of the device structure on the pulse pressure waveform was obvious. In the future, a more ideal impulse pressure waveform can be obtained by optimizing the device structure.