Abstract: The paper analyzes the reason why the pulse top spreads and the rise time shortens in a fault experiment on long pulse high power linear transformer microwave driver. Effects of waves superposition delay are discussed based on current transmission model. Output pulse waveforms are then derived by three dimensional simulation on the experimental prototype under excitations of different time sequences. The result suggests that, if the module closest to the diode is the first module physically, the delay from the switch triggered can be offsetted by waves superposition delay, and thus the wave optimization can be realized.