Abstract: Theformationmechanismofultrasonicstandingwaveswasinvestigatedthroughtheoreticalstudyandexperiments.Theformationofmicrostandingwaveswasobservedbymicroscope;atthesametime,thetheoreticalandexperimentalvaluesofthewavelengthwereanalyzedatdifferentfrequencies.Theinfluencesofvibrationfrequencyonthewavelengthofstandingwavesandtheamplituderequiredtoformthestandingwavewerestudiedwhenemployingdifferentpropellants.Theresultsshowthattheoreticalandexperimentalvaluesofthewavelengthofstandingwavesareingoodagreement.Thewavelengthandamplitudeofthestandingwavesdecreasewiththeincreaseofthevibrationfrequency.Whentheviscosityofthepropellantislarger，theamplituderequiredtoformastandingwaveisgreater.

Key words: ultrasonicelectrospraypropulsion, microstandingwaves, vibrationfrequency, wavelength;amplitude