We report the Doppler shift of Na spectroscopy changing with the slow wave factor in a slow wave microwave field the reason of the phenomenon is discussed. The varity of the Doppler shift of the Na spectroscopy in a slow wave microwave field was observed experimentally, the spectroscopy at slow wave factors of 10.67 and 5.20 were respectively. It is demostated that the Doppler shift is direct proportion to the slow wave factor in the slow wave microwave field.